I'd love to be able to set weekly goals around heart rate zones. For example, I'd like to have a goal of 150 minutes per week in Zone 2. Normally this would be easy enough simply by walking, the majority of which would be zone 2, but due to an injury I can't actually walk for exercise.
I'm able to achieve a zone 2 heartrate from a number of other activities but I have to go through each of them in the week and add up the zone 2 component to see if I'm reaching my goal. Having this calculated and tied to a goal would be a real time-saver.