Our bodies are so spectacularly complex we can measure our heart rate on different limbs without always reverting to a Care Bear's favourite major organ, which is why the Myzone MZ-Switch fitness tracker can attach to your arm and wrist as well as your chest. It's claimed to be the world's first interchangable heart rate monitor that combines PPG and ECG technology to keep tabs on your dicky ticker whilst working out, and because you have the added convenience of swapping the sensor between body parts you can choose the right place to pop it for the activity you're undertaking. For example, a chest or forearm reading will always offer greater accuracy for wrist-intensive workouts (keep your jokes to yourself, please), but swimmers and runners might find wearing it as a watch more comfortable. Packed with patent-pending tech and a gamified activity tracker app aligned to the World Health Organisation's guideliness for weekly fitness, it also puts the 'fun' into fundamental wellbeing. Available with aqua, grey, purple, and black straps, the Myzone MZ-Switch (£139.99) is out now, lasts for up to six months between charges, and is compatible with Android, iOS, Apple Watch, Wear OS, Samsung's Tizen, Strava, Garmin, MapMyRun and Apple Health.