Johannes Rukaber — freelance mobile developer, React Native apps and jrdevdesign portfolio

Heat Pump Control is a mobile app for controlling and monitoring heat pumps, including setup, status insights, and device control workflows.

Voice Journal is a private voice diary app for iPhone and Android. Record entries, get automatic transcription, and keep everything on your device — no account, no cloud.

Body Composition Tracker helps you measure body fat and lean mass from caliper readings, track progress over time, and keep all data local — available as a mobile app and web app.

TradingLog is a trading journal app for iOS and Android that helps you document trades, build discipline with checklists, and analyze your performance with detailed statistics.

PurePower is a local cycling power training journal for Android — record rides with BLE powermeters, track NP, IF, TSS, and FTP, and keep your ride history on the device with no account.

Bike Power Field is a Connect IQ data field for Garmin watches and Edge computers that displays live ANT+ bike power and cadence, especially useful on devices without native cycling power support.

Lifter is a simple workout tracker for Android with no ads, no account, and local data storage — track lifts and progress across many training disciplines.

dChallenge is a decentralized application that allows users to create and participate in challenges. You can bet that you will achive a certain goal and others have to confirm it for you to get your stake back.

Power Quote is an Android app to save quotes from books and websites, organize them with tags, and display them on your home screen widget.

next market is an NFT marketplace on which the files themselves are stored on the Arweave blockchain and are therefore immutable.

Internal job pipeline with n8n scheduling, RAG-assisted local LLM review, documented security controls, and Playwright E2E on Lifter — case study for automation and QA freelance work.