In the period between taking delivery of my Fitbit Blaze and working out how to charge it, I promised the smartwatch to five people: my son, my daughter, my friend with high blood pressure, my mister with poor sleep patterns, my other friend with gout. After a week, you’d have had to prise it from my cold, dead wrist. It’s compelling; it’s behaviourally… well, not transformational, but definitely nudge-y; it has lots of functionality that you didn’t think you needed until you had it; and it looks snazzy.

The headline use is for counting steps: ballpark, you’re supposed to do 10,000 a day, but I think that’s like eight glasses of water or five portions of fruit and veg, a figure made up by some people in a meeting who have totally lost patience with finding consensus on the actual figure. If you have a dog this is, in every sense, a walk in the park. It’s not unusual to clear 20,000. It’s also got GPS, to map your movements, and a built-in heart-rate monitor. You’ll need a smartphone to make the most of it, but that won’t be a problem for the kind of person who buys a Fitbit (the Blaze starts at around £150).

Use the “exercise” function, get on a bike and the Blaze will tell you your top speed and how many calories you used (you can use it for running as well, but I don’t). Between the phone and the Fitbit, you can also keep a food diary, which yielded the unwelcome news that I get an epic proportion of my calories from alcohol (last Tuesday, 53%) and that I eat like a German prince (hard cheese, 100g; sausages, five; bean stew, pot).

“Relax” gives you a two- or five-minute exercise of watching a dot go in and out and following it with your breathing. If you think of all the other things you might do with 120 seconds (check Facebook, get into a fight on Twitter, pace around, stare out of a window) this is more relaxing by a factor of about a thousand.

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The sleep monitor is the revelation; it charts the night and splits it into deep sleep, light sleep, REM and awakitude. I don’t know why it’s interesting, since there’s very little you can do to influence it; but somehow, the knowledge that you’re in a good mood because you only spent 33 minutes awake and 22% of your sleep was deep fosters a sense of triumph. I don’t know if this is universal – I congratulate myself for everything.

The stopwatch and countdown functions are intended for working out, but I timed myself doing everything, which put me on a constant achievement high, having emptied the dishwasher, filled it again and comprehensively relaxed in under 10 minutes.

I drank more water. I cycled faster, and more often. I didn’t go to bed any earlier, but I frequently pledged to. My wrist vibrated constantly with the sound of some fresh attainment; and I would not part with this device for all the cheese in Bavaria.

What I learned

A constant heart-rate monitor alerts you, incidentally, to the most stressful points of your week. Mine was trying to ice a cake in the shape of a guitar.

