Didn't know about this; are Edinburgh crossings fitted with these?:
http://www.bbc.co.uk/news/blogs-ouch-22706881
"The cone isn't telling you it's safe to cross, it's telling you the light is on. For instance, cyclists like whizzing through crossings sometimes, even though they shouldn't."
I know that some crossings in Edinburgh could be operated with a special yellow plastic key. I remember seeing this demonstrated when I was a kid.
But...
Can't remember exactly what it did (made a noise?), or how many crossings were fitted like this. Perhaps it was just a trial that never went anywhere.
(Ok, so as anecdotes go, this wasn't a very good one...)