A fortnight with…

Matrix Powerwatch X

£263.80, www1.techinthebasket.com

DAY 1 The chief innovation in this watch is that it’s powered by your body heat, using thermoelectric technology, so it never needs charging. This is very impressive.

DAY 2 It’s rather heavy and a little cumbersome – it may be too chunky for runners with small wrists.

DAY 5 Offers steps, stopwatch and calorie-burn functions. A ‘run mode’ measures distance but only using an internal accelerometer, which is about 85 per cent accurate. DAY 6 Message notifications are frustrating: they tell you who has messaged but they don’t display the text.

DAY 8 The calorie-burn function seems accurate when compared with numbers from other devices. However, the sleep functionality is exasperatingly variable – it works on some nights but not others.

DAY 11 Haven’t worn the watch for a couple of days but stored power and data are saved for 12 months without you wearing it.

DAY 14 Verdict: this is a vision of the future of these devices, but it needs to be further developed. It will do the job for early adopters who are casual exercisers, but it is probably not sophisticated enough for keen runners. ••••••••••