Oura is a ring worn tracking device that can tell you your HR, HRV, RR, sleep cycles, and has further metrics around stress, and so on. Surgeons often like it because it’s a plain band, so you can usually scrub with it. It’s also got nice aesthetics and a helpful app.

Approx cost for device = £250-500 
Subscription = £5.99 per month or £69.99 per year.