We use a Nest thermostat and two external cameras as our house is empty most of the time. Thermostat set to 20 (adjustable remotely, as is the hot water). The cameras record either people or other movement, if you wish, then ping you on the phone with a video history. Our plumber came round yesterday, so the camera alerted me, for example. It also lets you have a two-way conversation with anyone outside. All this from 11,000km away! I got a Nest fitter to put ours in, and just as well as the existing thermostat was 'wrongly wired' and it took him a while. Cameras also installed by a fitter, as required rodding through the eves/high ladder work. Higher cost, but worked for two years, only stopping with power cuts but instantly up with power resumption. Edited to say we might not use Nest if we actually spent more time in it!