If the devices are ANT+ compliant, then you only need an ANT receiver and a profile decoder since HRV is output on one of the background pages. That should be doable with pretty much any Nordic microcontroller. Otherwise, most devices will have BLE as you noted, but I don't recall if there is a public characteristic for HRV. There probably is, but I just don't remember.
This is really not the place to be taught how to interface with BLE. Find a good tutorial, since the details can be important.