Sony SWR12 Smart Band
What's nice about the SmartBand 2's optical heart rate tracking is that there's lots of choice over how you want to use it. Double tapping the tiny power button on the right hand side of the tracking module puts the band into continuous HRM mode, the battery life for which you'll get ten hours. It's quick and not at all fiddly to press this at the start of a run or workout and the strong vibrations indicate immediately that it's kicked in.
Otherwise, the SmartBand's stated two day battery life is based on heart rate tracking 5 - 6 times per hour, including when you are asleep. Stamina mode which gets you five days turns the heart rate sensor off entirely.
It's a nice solution to cater to different levels of user and the readings we got at rest and during exercise are within 5 - 10 bpm of a chest strap. So that's not perfectly accurate but it's similar to the results you'd get from a accurate enough for beginners looking to see, for instance, their resting heart rate go down as they get fitter.
The stress and recovery metrics, measured by your heart rate variability, are more difficult to test but low stress periods did correlate to an hour of sitting down working and medium/high stress periods logged to exercise. The graphs and timelines could be incredibly useful here if you're looking to reduce your stress levels and it's fascinating stuff.
The main difference between this tracker and its predecessor is the heart rate monitor. Returning are the vibration alerts for calls, texts and notifications - which are not very subtle - a smart alarm wake-up feature and an out of Bluetooth range alert so you don't use your phone. So far, so standard, so 2014.
The apps you are alerted to can be customized in the SmartBand 2 app but there's no contact or keyword control. Somewhat obviously, there being no display, the tracker also won't tell you the time or weather or anything like that either. Plus your steps, distance, time spent active and estimated calories burned are all access via apps, not on the band. It's worth mentioning that it is compatible with Google Fit on Android and Apple Health on iPhone.
Pairing can be done via good old-fashioned Bluetooth of NFC if your smartphone has the tech. Apart from some basic media controls - you can set the button to play/pause and skip music if you wish - that's it for non-tracking features. Still, chances are you're not considering buying this as an alt-smartwatch.