This is brilliant. Thanks so much for doing an API! As much as I like web apps, I'd hate to keep a tab open for the entire day in my browser. I'll go build a simple native mac app that sits in the toolbar and plays music.
The fact that the points are arbitrary I think prevents someone from finding ways to hack or optimize it. If it counted calories, then you would look online for the best ways to burn calories. If it measured heart bpm, then you would find ways to cheat that.