1. Polar H7
Polar's H7 heart rate monitor is another competent bit of kit capable of keeping an eye on what your heart is up to. It is compatible with an iPhone 4S or later and various Android devices, while its ability to work while you swim is another bonus. Plays nice with the Polar Beat app, too, and other fitness app alternatives so you can really delve into your activity.
£64.50 | Polar