Does anyone use a fitness watch while playing tennis?

I'd love to hear your experiences. Specifically, which watch are you using and are you using it in conjunction with a 3rd party app that gives extra information?

I'm in the market for a way to track my mileage & heartrate while playing matches and would love to hear how other people are doing it. It looks like I would need a watch with stand-alone GPS (not "GPS compatible" aka you need to keep your phone on you while playing). But what about tennis specific apps?

I've read about the Babolat bracelet (and racket), and seen people posting on forums about tennis apps that integrate with their watches (but have issues exporting data).

Thanks!