I worked on the predecessor to Hive back in about '08-'10, the engineering consultancy I worked for designed a version of the "hub" and a number of their security and energy monitoring sensors.
It was the first thing I worked on that made it out into consumers hands (v2 of the hub). I remember one day buying a copy of Wired magazine, and it had an article about them. Seeing a product I had designed in that magazine was a really memorable moment.
Back then they were not part of British Gas but a Cambridge UK startup called AlertMe. A really good bunch of people with a vision for the smart home. The plan was clearly to start with the security products, then energy monitoring was a secondary market. However after getting a big contract with British Gas to supply monitoring to all their customers, they pivoted almost completely to that - and ultimately they were acquired by them.
As I said, they were a really interesting team, their CTO was a former early Acorn employee who had lead RiscOS.