I really hopes this comes soon. It'd be even better if you can have it so the screen shows if you're in the correct zone during the 4 minutes. Ideally, take the functionality of the "calculate your heart rate" page so you can figure it on the app, set it using those recommendations then monitor and indicate when you're on target. Without this HR functionality, it's nothing more than an interval timer, and I already have a good (free) one. Any ETA on when this might come?