Flex

Flex is an offline-first workout tracker for strength training and cardio, released under the MIT licence and built with Flutter. You build plans per weekday, schedule exercises into them, and log each set as either weight and reps or a cardio effort with time and distance. A rest timer runs between sets, on Android as a foreground service with a notification so it keeps counting when the app is in the background or the screen is off. Progress is read from graphs rather than a dashboard: every exercise keeps its own history and chart, and the graph screen can overlay records, merge several exercises into one chart, and show a global progress view across your training.

Everything lives in a local SQLite database through the Drift ORM. There is no account, no server and no sync service, and the Android manifest requests no internet permission at all, so the app cannot phone home even if it wanted to. Data leaves the device only when you ask it to: graphs and plans export to CSV, a full backup is written as a zip archive containing the database and your exercise images, and that archive or a raw SQLite file can be imported back. The interface ships in 27 languages including right-to-left Arabic, Farsi and Urdu, and the theme follows Material You dynamic colour from the system wallpaper. Flex is published on Google Play, F-Droid and the Microsoft Store for Windows, and a Flutter web build runs at brandonp2412.github.io/Flex.

Compared with Hevy, Strong, Fitbod, JEFIT and FitNotes, the difference is ownership rather than features. The commercial trackers keep your routine and history in a vendor account and sell subscriptions or cloud tiers on top of it; Flex keeps the same kind of logging and graphing on the device and asks for nothing. The trade-off is that there is no built-in cloud sync or multi-device hand-off, so moving to a new phone or a second machine means exporting the backup archive and importing it on the other side, and you are responsible for keeping that archive somewhere safe.