Until my graduation from high school, I was working avidly on an app to have the substitution schedule of my school in my pocket, through an app. At its peak, the app had hundreds of active users at two local schools, but has been discontinued.
It used to be available both for iOS and Android.
The Android app can still be found at https://play.google.com/store/apps/details?id=com.ops.app.
The app comprised three parts, 1) a server, 2) an uploader, and 3) the app itself.
A teacher would create a new substitution schedule, that was automatically synced to the server with the uploader.
The app users could then access their personalised schedule from the server.