The last discussion about this topic I found was Jim saying that HR straps don't generally supply battery info. Garmin's latest HR straps do.
For some reason, CIQ supports Cadence, Speed, Power, Radar, Lights and Shifting. But there still is no class to listen for messages from (or an ability to poll) ANT+ HR straps, to get info like battery status. Kinda of a glaring gap. HR sensors are probably THE most common external sensor. Yes I get that some HR data comes from optical watches, some data comes from BLE. That's fine. There should still be support for the ubiquitous ANT+ external HR sensors.
If anyone from Garmin monitors this forum - consider adding HR support like you already do for almost every other common (and uncommon) ANT sensor. Thanks!