[feature request] HRM ON only during activity/training, NOT just alwaysOn OR never

right now you can only set the HRM always on (with the annoying green flickering in the dark and battery drain) or you set it OFF, but then the HRM is not availble neither during activities
I think the HRM should work like the ecompass......you only switch it on when you want to
off course the h24 on mode should still be available, but only for those who want to