Garmin heart rate monitor straps are very high quality, but quite expensive. Polar HRM straps (Polar SoftStrap) are a more modestly priced alternative. They are compatible, but have to be modded a little bit.

Have you ever found yourself navigating with your smartphone while you really would have rather used that cool wrist-worn GPS device, but you forgot to upload the waypoint beforehand? No more embarrassing moments like that, because now there is IQMapReceiver.