Total Time in Heart Rate Zones by Week, Month, and Custom

Many training programs are built on time spent in different heart rate zones. It would be fantastic to be able to view the time spent in each heart rate zone for a given period of time (week, month). Even better if you could look at a custom timeframe to know how many more hours you had left in a zone for that week.

I am an endurance athlete that uses common training methods set out by Training for the New Alpinism, the bible of mountaineering training. I am sure that this is something MANY users would find useful.