For a while now I've been looking at sleep trackers with an eye to try improve my sleep by working out ideal sleep lengths etc... I've been using sleep as android on my phone, which seems quite feature packed and I love the smart wakeup feature but I'm dubious about the tracking accuracy. I rarely sleep through the night and have to get up to go for a wee a few times, sleep as android doesn't ever seem to detect this as awake time. Understandable as the phone just lies on the bed so just sees a flurry of movement then stillness, another flurry then still again. The very best trackers are upwards of 100 quid and even general fitness bands that also do sleep tracking tend to be ~£80 and a lot of them sleep tracking seems like a bit of an afterthought. The Jawbone UP3 appears on a few sleep tracker rundowns as one of the better bands for it, although it has a closed API so won't integrate with other apps and I think that it was recently bought out and the buyer said they won't be releasing any further updates (could be something else though). It does have smart wakeup and things like that though. Anyway, I found a seller on ebay selling the UP3 for £40 new but without packaging. £40 is just about the maximum that I've been willing to flutter on this as it's almost about interest as anything else. Being able to track the number of times I wake up during the night could prove useful though. Today it arrived, it's reasonably small and seems pretty simple to use. Three LEDs show various things such as mode and various notifications. The app was pretty simple to setup and seems to have everything that I need, it also does things like step tracking and monitors heart rate. I'm not overly interested in step tracking, passive heart rate could be interesting though. Whilst the band doesn't actively monitor heart rate it does have what it calls passive monitoring. This means that it samples heart rate at various points during the day, this is supposed to assist with showing the effect of hydration, stress etc... on heart rate. It also works out resting heart rate by sampling heart rate when you wake up. I suspect once the novelty wears off I may stop wearing it during the day, we'll see. One other thing I really like is that you don't have to tell the app when you're going to sleep or wake up, it just detects it. EDIT: After 1 night sleep it does appears to work quite well. I took note of the times I started to try to sleep and what time and I woke up and the tracker was pretty accurate on times. It monitored deep sleep, REM, light sleep and number of wake ups and time awake. 2h27m deep sleep, 3h5m light sleep, 1h14m REM, 39m awake (this is including a period of time where I just lay in bed and didn't really get up, it appears to show this period on the chart as awake too which is quite cool) and 2 wake ups. Obviously I have no idea how accurate the sleep lengths are, but the awake feels like it's about right and the wake ups is correct too. I've just noticed it tracks passive heart rate during sleep too and displays a chart of overnight heart rate and RHR across the week which is cool if you're a nerd for basically useless data like I am!