Re: What a stupid fucking idea....
It needs a bit of care both ways. Of course this system will not work on the windy country lanes in $NationalPark where there is no data connectivity and you can't see round the bend. Takes the cyclist to assume that drivers won't see them til the last minute and be able to take avoiding action, and the driver to be driving such that he/she could stop safely.
This goes as well if the warnings are too frequent they will be ignored, far from the other distractions that could be encountered en route from "sat-nag", phone etc.
There are idiots behind wheels and on saddles, you just have to assume you're going to come across them. However go the other way, if a driver lets you pull out or in other ways behaves well, a friendly wave is appreciated. The driver who ignored you is just going to ignore the unconventional hand signal you want to give him anyway - don't bother it's not worth it.
Yeah, I am both a cyclist and a driver.