One person, 16 apps, 43 books

Apps, books, and tools that respect your attention.

JC Mobile App Studio is an independent studio run by one developer. The apps run on-device and never track you, the picture books explain how things work, and the journal says what I actually think about tech, money, and privacy.

Browse the apps See the books

14 apps on the App Store
1 in review
43 books on Amazon
315 articles
45 free tools

Start here

DayCast

DayCast keeps your whole day in one private place. Plan your day, capture notes, journal, track spending, and mark up PDFs, then pick up where you left off on iPhone, iPad, Mac, Apple Watch, or any browser. Your data is encrypted on your devices before it syncs, and there is no account to make.

See DayCast

Meet Vera

VeraCast

The weather app that talks like a person, with a companion who dresses for the day. Vera floats beside your temperature in one of nearly 50 looks that follow the real weather, from a popsicle at 91° to a snowman at 28°. She blinks, smiles when you tap her, and pouts when it rains, and you can ask her anything about your forecast. Every morning VeraCast writes you a plain language briefing in your own tone, then backs it with animated radar, National Weather Service alerts, and warnings for earthquakes, hurricanes, pollen, and UV. Nineteen activity outlooks score the next ten days for what you actually do, a Pet Walk card tells you at a glance whether it is a good time to walk the dog, and a daily horoscope rounds out the ritual. No ads, English and Spanish.

See VeraCast

Three in one

WavCast

One app for podcasts, live internet radio, and local news. WavCast streams directly from open, public sources, the Podcast Index and podcast RSS, the Radio-Browser station directory, and public news feeds, so it hosts nothing and locks you into nothing. Ask any episode a question, read along with synced transcripts, and take it to the car, your wrist, and iPhone Duo. Free, with an optional Plus subscription and a one-time purchase to remove ads.

See WavCast

Proof, not promises

ChoreSight

ChoreSight is a household chore tracker built around accountability. A chore isn't done until someone submits a live photo of the finished work, skipped chores turn red and lock to the top of the screen, and any family member can take over an overdue task. Parents review and approve every submission from one dashboard.

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ChoreSight on iPhone, iPhone Duo and iPad

Built for Apple Pencil

Libreto

Libreto is a full drawing studio, digital notebook, planner, and PDF editor for iPad and iPhone Duo, and a streamlined PDF editor and notes app for iPhone. On iPhone Duo, notebooks, planners, and PDFs open as two pages across the fold. Sketch and paint on a layered canvas, keep linked, dated planners, mark up and sign PDFs, ask questions about any document and get answers with page citations, and search your handwriting on device in 20+ languages. Your files stay in step across every screen through your own iCloud. Every tool unlocked for $19.99 a year, or $59.99 once, no tiers, no upsells.

See Libreto

The lineup

Every app, at a glance

Tap any app for the full brief: screens, features, and the download link.

See the full lineup, with screens

How it's built

No tracking. Ever.

The same three rules in every app, every book, and every tool.

On-device by default

Apple's Foundation Models do the work locally, so your notes, receipts, and health data are understood on your iPhone, not on a server. Where an app syncs or uses a cloud fallback, its own privacy page says so in plain words.

No tracking, ever

No analytics SDKs, no data sold. One app, WavCast, runs ads in its free tier and says so upfront, with a one-time purchase to remove them. That is the whole list of exceptions.

English and Español, day one

Bilingual is a feature here, not a translation bolted on later. Plantilla goes further and speaks ten languages, because the people who need it do too.

The books

Same studio, different medium.

I write picture books for the same reason I write apps: most things are explained badly. A storm is water and air doing loud work. Sleep is a whole crew on the night shift. 43 titles on Amazon in print and Kindle, most of them in four-book series.

All 43 books

The Wobbles Series · 4 books · Ages 3-7

Wobbles are wiggly little worry-creatures only Mara can see, and they grow bigger every time she keeps them secret. Each book puts her in one specific nervous moment, a new school, a sleepover, a checkup, a stage, and finds the same fix: say it out loud.

Three Dogs, One Park Series · 4 books · Ages 3-7

Luna, Sophie, and Joy are real dogs who share a real backyard with Joe. Each book pairs one park-dog moment, a storm, a vet visit, a new puppy, with a friendship or big-feelings lesson for kids who love animals.

The Goodbye Button Series · 4 books · Ages 3-7

It started as one small ritual: Mom draws a purple sun on Josie's palm and on her own, press yours and mine buzzes. Then it turns out the same trick, a tiny hand-drawn button and a grown-up's steady explanation, can be redrawn for whatever a kid is actually facing, a first sleepover, a scary new skill, a mistake that feels too big to fix.

Book and app pairings

Three Dogs, One Vet Day

VitalLedger, the vet visit in the book is the record you keep in the app

The Night Shift

Steady, a bedtime story about sleep crews, and a sleep planner for people who work nights

Where Did My Dollar Go?

DayCast, money explained for kids, and a spending tracker for the grown-up reading it

All 43 books

The journal

Tech, money, and privacy, explained plainly.

Honest reviews and plain-language explainers from the same desk that builds the apps. New pieces most days.

All articles

A kitchen table in the morning, an iPhone showing a Zelle payment confirmation inside the Chase app next to a Google Pixel showing a Venmo transfer, a paper bank statement, reading glasses and a mug of coffee

InvestingAI

Fintech money is back, $103 billion of it, and a fifth went to AI. What the KPMG numbers say, what $541 million bought last week, and the fraud problem that comes with instant payments

KPMG counts $103.1 billion of fintech investment in the first half of 2026, with $21.4 billion into AI-related fintechs, on fewer deals overall. Last week added $541 million across 16 rounds, led by Whop at a $5.1 billion valuation, and Nasdaq's fraud-detection unit grew 23 percent. The euro area's instant payment deadlines, the voluntary FedNow, the FTC's $15.9 billion in fraud losses, three corrections, and what it means for your bank app. Verified October 25, 2026.

Josuam Collazo · 6 min read

A Samsung Experience Store in London, a Galaxy Z Fold8 and a Fold8 Ultra open on a white display table under spotlights, a customer folding one, an Apple Store visible across the street through the window

TechAndroid

Samsung says Fold8 sales are up 45 percent in Europe. Whose number that is, what the iPhone Duo has to do with it, and the rest of the week in Android

Samsung's own UK release says the Galaxy Z Fold8 and Fold8 Ultra together outsold the Fold7 by 45 percent in Europe over nine weeks, and that searches for its foldables jumped 460 percent the week Apple announced the iPhone Duo. What the number does and doesn't say, Fold8 prices today, a Pixel caller ID option found in an app teardown, Galaxy Buds On on sale in Korea, and Nothing's Pokémon teaser. Verified October 25, 2026.

Josuam Collazo · 5 min read

A Nintendo Switch 2 in handheld mode held on a train, the screen showing a Call of Duty multiplayer match in a rainy city street, Joy-Con 2 controllers attached

TechGaming

Modern Warfare 4 on Switch 2: what's been measured, what hasn't, and why the port matters more than the game

Call of Duty: Modern Warfare 4 launched Friday on PS5, Xbox Series, PC and Switch 2, with an 86 on Metacritic and no Game Pass until late 2027. The Switch 2 port targets 30fps in the campaign and 60 in multiplayer, but nobody has published a full frame-rate analysis yet. What Capcom actually said about Monster Hunter Wilds, September's PS5 and Switch 2 sales estimates, AMD's FSR 4.1 on Xbox with no date, and Sony's QSSR. Verified October 25, 2026.

Josuam Collazo · 5 min read

All articles

Free to use

Small tools, no signup.

The same thinking as the apps, in 45 calculators that run entirely in your browser. Nothing is saved, nothing is sent.

All tools

Pet Kit 5 tools in one app

Pay Kit 8 tools in one app

Money Kit 8 tools in one app

Body Kit 7 tools in one app

Phone Kit 12 tools in one app

Install any of them to your home screen. They share what you enter and work offline.

/tools/final-paycheck Final Paycheck Calculator Last hours, overtime, unused PTO, and when your state says it is due. Open → /tools/free-trial-deadline Free Trial Deadline The exact cancel-by date, a reminder, and a calendar file. Open → /tools/ios-beta-calendar iOS Beta Calendar Latest betas, expected RC and release dates, and what your next update is. Open → /tools/pay-stub-decoder Pay Stub Decoder, EN + ES Every line on a US pay stub explained in plain English and plain Spanish. Open → /tools/bedtime-by-age Bedtime by Age A bedtime window from wake-up time and pediatric sleep guidelines, naps included. Open → /tools/vaccine-schedule Puppy and Kitten Vaccine Schedule A dated core vaccine timeline from the birth date, with a calendar export. Open →

All tools

Who builds this

One person, nights and weekends

I've been hooked on tech since my first Compaq and AOL dial-up, and I was the one family and friends called to fix their computers. By day I work in HR. Nights and weekends I build the apps, write the books, and publish the journal, all drawn from problems I actually had. No hype, no affiliate bait, just the stuff I would want a friend to tell me.

Josuam Collazo Designer & Developer, JC Mobile App Studio Learn more about Josuam

Apps, books, and tools that respect your attention.

DayCast

VeraCast

WavCast

ChoreSight

Libreto

Every app, at a glance

No tracking. Ever.

On-device by default

No tracking, ever

English and Español, day one

Fintech money is back, $103 billion of it, and a fifth went to AI. What the KPMG numbers say, what $541 million bought last week, and the fraud problem that comes with instant payments

Samsung says Fold8 sales are up 45 percent in Europe. Whose number that is, what the iPhone Duo has to do with it, and the rest of the week in Android

Modern Warfare 4 on Switch 2: what's been measured, what hasn't, and why the port matters more than the game

One person, nights and weekends

Get in touch.