Puls8 chest arm bands connect via bluetooth to any android or apple device. This is the perfect way to track the intensity of your workouts whether it is in the gym or out for a run.
The free Android and Apple app allows you to track the times spent in the various training intensity zones.
You can download the android app here: https://play.google.com/store/apps/details?id=com.onecoder.puls8
Or the iphone app here: https://apps.apple.com/ie/app/puls8-fitness/id1495122077
Product comes with a 12 month warranty.