It's customary to be dismissive of anything like that in these hallowed halls, but one of the major issues for all these odd "safety" measures such as this, odd stop lights, indicators etc has always critical mass of takeup leading to driver understanding.
The fitting of these lights to the hire fleet has created that critical mass in London, and actually they are pretty good, as they say "cyclist coming" from a few meters back, helping visibility especially at junctions. Likely as not useless elsewhere in the UK, but there you are.