Which is what everyone needs to consider. They may not be as accurate as people might want, but they track to relative accuracy, and provide a motivator. For £20, that's a lot for your money.

As long as you have an Android or Apple smartphone, then yes. There is a free app called 'Mi Fit' available for either platform.

Yes of course, sellotape or Velcro are the preferred option, stay away from screws and nails.

In both cases, those issues can be resolved by different software. I agree the Mi Fit app is quite poor, the worst thing for me is it wanting to display my weight on the screen when it's got no means of measuring it!! If you get 'Mi Band Tools', its a lot better and gives you extra heart rate features. And for some reason it's a whole load quicker taking your heart rate, which sounds really odd considering it must be hardware rather than software related.

It's still not perfect, for example every so often my heartrate shoots up to 220 and then straight back down. But the graph shows this occasional doubling of numbers, and holding down on the offending item deletes it to give a more consistent graph. And you're still dealing with a wrist based monitor, that simply cannot compete with a chest based one. But none of them can.

The only thing I see as a negative for Mi bands is that they're not accepted as a 'standard'. If you have a fitbit or other 'known' brands, you can join groups and have competitions etc (my work has a league table for exercise). I've not yet figured out how to get a Mi band to join in.

It stores it in the band's memory - the earlier models could store around 10 days of activity, so I imagine it's the same with the Mi Band 2