In the latest version of the Group Fitness Plus for iPad we have added support for the latest Polar heart rate monitors, Polar activity trackers and sport watches with optical heart rate monitors.
With the application you can use the Polar H7, the new H10. The Polar A360, M200, M430, M600.
The Group Fitness Plus for Android is compatible with any ANT+ HRMs devices in the market. More than 80 different heart rate monitors.
Check this link for a comprehensive list.
With the Group Fitness Plus for Android you can also use activity trackers with optical heart rate monitors from Garmin, like the VivoSmart HR. Garmin sport watches with optical heart rate monitors like the FR225, FR735XT, FR935, Fēnix 3 HR, Vivo Active HR, Fēnix Chronos, Fēnix 5. And Mio devices, and Scosche Rhythm+ arm bands.