It would be nice to set fitness trackers and reminders. Nothing crazy, just a simple way to have an overview of your activities. You can plot just about any biometric or nutrient value, why not have somewhere that tracks the activities you input? (or maybe I'm missing it) I know you can add the exercises as custom biometrics, which I suppose could work.
My other thought is if exercises are tracked, add in a reminder as well. Such that, if a user has a goal specified of 3 hours of yoga each week, or 30 minutes of yoga each day, etc., give the user the ability to set up reminders to do yoga. Also, for desk workers like myself, have a reminder to get up and walk at predetermined periods.