Google Nest Thermostat
The Google Nest Learning Thermostat is a fantastic device that replaces an existing central heating thermostat and/or programmer, and controls your home's heating and hot water in a smart, energy-efficient way. It helps save money by monitoring your boiler usage and allows you to control your heating remotely using a simple smartphone or tablet app (iPhone or Android).
Due to the significant differences between UK and North American heating systems, Nest recommends that the UK editions of this device are installed by pro installer.
I'm a trained Google Nest Pro Installer, for both their thermostats and smoke/carbon-monoxide detectors. Below is a photo from a Google Nest (3rd gen) Thermostat installation that I carried out recently (replacing a very old Honeywell mechanical rotary room thermostat).