I'm working on a workout API and native apps (iOS/Android) for Strength Level [1] as another interface for my.strengthlevel.com [2]. Strength Level helps you understand your relative strength - how strong you are for your bodyweight.

Using PHP Slim Framework, MySQL, and vanilla Swift/Java. Prioritizing reliability and efficient sync between local storage and server. Currently finalizing API endpoints and feature matching the web app. Next up is adding a subscription model.

It's challenging as:

- Users want to use the app offline which means we need to sync

- We have to match our existing features on [2] in the first version and evolve the API and database to support reliable sync

- Users want to also track their cardio too e.g. Running Level [3] and Rowing Level [4] but that will have to come out in a future version

[1] https://strengthlevel.com/

[2] https://my.strengthlevel.com/

[3] https://runninglevel.com/

[4] https://rowinglevel.com/