Aside the fitness tracking aspects they can also be helpful monitoring symptoms of chronic health problems. It took me a while to select a band, I couldn't decide between the Fitbit HR which gives constant heart rate readings thus being good for monitoring my POTS or the Jawbone Up3 which is good at monitoring sleep. In the end I went for the Jawbone.
The Jawbone offers quite a few features which I don't use, although I do find it interesting to see how many 'steps' I've taken. According to the app I've taken 100 today yet I've not actually taken a single one! It takes regular pulse readings which are often quite out from what my pulse really is, this isn't helped by me wearing it too loosely but even so it would be better if it was more accurate. 2 features which I haven't tried yet but will are the 'idle alarm' which you can set to go off if you have been still too long and a smart alarm that wakes you during a light phase of sleep. It works by gently vibrating on your wrist. The idle alarm is meant to encourage you to get up and exercise but seeing as I'm meant to change position every half an hour or so then I think it could be useful for that. I'm going to try the smart alarm to see if I wake up any less groggy.
As for sleep tracking, I've found it helpful. It's taken me a while to get used to it and some days it still only captures part of my sleep but here is one 24 hour sleep period analysis.
It says I slept for a total of 10 hours and 30 minutes, of which 33 minutes was deep sleep, 4 hours 15 minutes was REM (no wonders I had vivid dreams!) and I woke up 6 times resulting in being awake for 1 hour 35 minutes.
I'm not sure of the benefit of all this information for healthy people but it's enabling me to see what sleep medications have what effect. I've learnt from this that the best combination for a good mixture of light sleep, deep sleep and REM is 40mg Amitriptyline (I've had to drop down to 40mg from 125mg after suddenly becoming sensitive to it), 11.25mg Zopiclone and 2mg slow release melatonin. On the night the above was recorded I had 40mg Amitriptyline and 7.5mg Zopiclone. A friend is experimenting with supplements that aid sleep and is finding the Jawbone helpful, especially when a supplement increased his REM but decreased his already tiny amount of deep sleep.
I'm disappointed that where it hasn't always recorded day time sleeping I've not managed to catch any of my odd sleep problems on it (paralysis, hallucinations, drifting in and out of awareness etc) but I'm hopeful it will capture that soon.
As for comfort for wearing, it's not too bad and I'm adjusting (my skin is very sensitive to touch). I wear it looser than your meant to and I don't wear it during waking hours although I'm slowly increasing the time I do wear it.
I paid £80 for mine from Amazon on Black Friday but there seem to be lots on offer. The Jawbone Up3 is the one that tracks sleep best from the Jawbone range.