Developer here. Thanks for checking out my app, Riker. In case anyone is curious, the iOS app is native, written in Obj-C. The Riker web app is written using React and Redux. The REST API is written in Clojure and the backend is Postgres.

Although there is also a fully functional web version of Riker, the app is preferred since it supports offline mode, provides Watch App and integrates with Apple's Health app.