Time in Heartrate Zones

[Gondwana]

I'm developing a watch face on which I'd like to include progressive indicators of the time spent in each heartrate zone so far during the day. However, I gather those running totals aren't exposed by the on-device API. Am I correct?

(I know I could get it via the web API but this would be very laggy unless the device is synced very frequently, which mine isn't).

Would I be able to construct the info myself using a companion app to tally up the data even when my watchface isn't being displayed? If so, would this be a disaster in terms of battery life?

Thanks!

[Gondwana]

Having done a little more digging, I gather that a companion app won't help because it won't have access to the device API (needed to get heartrate). However, the clockface app itself may be able to still receive heartrate updates even when not on screen (eg, during activities or when an app is running).

Am I on the right track?

(It would be kinda nice if the firmware and device API could be modified to maintain and provide a tally of time in each zone, rather than doing the calculations retrospectively in the web API. Would such a feature request be smiled upon? It would be easy to do!)