Is there a way to collect heart rate and step data continuously in the background?

A background service can run at most every 5 minutes and run for a max of 30 seconds at a time.

Depending on your device, there are watch faces that will display "real time" heartrate all the time, which actually only changes every few seconds in many cases. 24/7 OHR is a bit different than the HR you see in an activity.  Peek under your watch, and if the green leds are flashing, you are in 24/7 mode.  If they are on solid, that's the activity mode.

Thanks for the reply! So is there any way for these watch faces to record the value rather than just displaying it? It seems a huge waste of energy to be measuring these things 24/7 but lose them simply by not writing them down…

Can a background service access more detailed recent heart rate and step event data to record it before it gets aggregated into the two-minute and fifteen-minute averages that are saved by default?

What device have you bought? My f6p measures HR/steps every second, temperature every minutes etc. There is no any aggregation, Maybe in sleep hours system exposes data less frequently.

It’s a Forerunner 255 Music.

How do you access your data recorded every second? If it’s like the Forerunner, though it polls the sensor far more regularly, it only writes that data occasionally so when you eg download it from Garmin Connect, it’s aggregated as I suggested in my question.

Do you want to

- fetch and analyse all day data or single activity data or 

- only shows actual data?

During an activity is can be rbe recorded every second, or with "smart recording" which will have gaps in the data.("smart" is the default on devices)

  Recording an activity uses more battery than just running a watch face

I understand that, but I’d still be interested in logging heart rate and steps more frequently during all-day tracking if this were technically possible, even if it comes at some cost to battery life. Is there a way to do this?

I want to collect all-day data at a higher frequency than it is currently recorded, to fetch and analyse later. It’s fine if it’s just recorded to the watch rather than Connect, if that helps?

So due to limit of CIQ app it's impossible because it means you have to write app and save data in background every 5 minutes and only for 30s. So you have 4,5 minutes holes and big impact on battery.

Maybe solution is taking fit files directly from watch file system.

And if you record a fit, the best case is every second and more of an impact on battery than a background service.