Looking for Heartrate chest strap

[Newtons Apple]

My neighbor has a 6+ and wants to track his HR and would like to know what the best chest strap HR device on the market. One that goes around his chest and works off of Bluetooth.

Anyone have any suggestions. He does not want the Apple Watch

 

[rocksyoursock]

I use one from Wahoo Fitness. I use it for jogging and gym workouts. I also use the Digifit app with it since it works well for Insanity and P90X style workouts.