If your greatest "achievement" this week was unlocked on your Xbox, the Fitbit Flex could be just the thing to drag you off the sofa and into the land of the healthy. This rubbery band taps into those gaming instincts but makes you work a bit harder for its virtual high fives. The Flex is a ?pill-sized sensor that slips into a comfy, rubberised wrist strap. It packs in – take a deep breath – Bluetooth 4.0 to feed your phone live tracking info, NFC to start the mobile app at a touch, an accelerometer, ?a week-long battery, a vibrating motor and a five-light display. Live tracking your steps on your mobile as you walk will certainly make you feel good, and whether on your phone or a computer you can set goals for distance, steps or calories. Five white LEDs alert you – at a tap – to your progress in 20% increments. The brains of the Flex unit are removable, so you don’t have to use the strap. You could even pop it in your sock for cycle tracking.