This is a Smart Thermostat which works with all (fairly) modern boilers with volt-free switching, and a much cheaper alternative to the Nest 3 (almost half price) and Hive 2, and performs the same functions. I have had this for 3 months (self-install) on my 12 year old Ariston combi boiler and has performed brilliantly so far. The system is very simple, comprising of the thermostat unit and a mains-powered relay which connects wirelessly to your router. This is the lowest price this has been at Amazon (see the three camels in first post), and possibly the lowest price brand-new anywhere in the UK - I couldn't find it lower anywhere else.
Amongst the nifty features of this system is full voice control with Siri or Alexa, and geofencing via IFTTT (If This Then That). You can install the system in one of two ways which provides greater flexibility than most of the other Smart thermostats:
1. Replace the wired thermostat on the wall, with the Netatmo switching the boiler directly, and the relay plugged in to a plug point as a simple wireless bridge, or
2. Use the Netatmo unit as a mobile unit powered by batteries with the relay taking over the boiler control - in this case you'd use the provided two sets of removable wires to connect the relay directly to the 240V boiler power and volt free switching terminals.
Either system allows full remote control functionality via internet-connected devices.
I did the latter installation and can take the thermostat with me around the house - as the thermostat is powered by two AA batteries and importantly, has an e-ink display, the batteries last for 6 months plus (unlike the Nest unit which needs to be plugged in on its mobile stand hence is not truly mobile). There is no router dongle like Hive - the relay interfaces directly with your router.
The Netatmo app on iOS and Android gives you full remote control and programming functionality, and detailed thermal analysis of your home. The 'learning mode' is pretty good as well. I use IFTTT for geofencing (boiler switches off if I'm 2 miles from home, comes back when I re-enter that radius): https://ifttt.com/netatmo_thermostat.
All in all, I've been very satisfied with the performance of this thermostat. The app works well with both WiFi and 3G/4G on Apple and Android devices, the signal has not dropped once during the three months I've had it, and it appears to re-connect seamlessly whenever the router is powercycled.
From the blurb:
37% less energy to heat your home. Save £312 a year on average*.
Control your heating remotely from your smartphone, tablet or computer, or directly on the Thermostat.
Control your Thermostat with your voice simply using Siri on iPhone/iPad or Alexa on Amazon Echo.
Smart heating: enjoy better home comfort with the Auto-Adapt and Auto-Care functions.
Unique design by Philippe Starck. 4 colours to choose from to suit your home interiors.
Compatible with gas, oil or wood-fired boilers and heat pumps.
Compatible with iOS, Android and Windows Phone.
(*average savings for a conventional 1076 sq ft British house with a gas boiler.)