I can't find any links now, but after Williams created the flywheel kers system, they started talking to the London train system, who was interested in adding it to a trains in the city. Not sure who that ended up.
It's worthy noting, however, that none of the two companies ended up running the flywheel kers in real races last year or this year. KERS was only one of the rule changes for those years, and those teams decided it was best to focus on the other changes instead.
Not related to the post itself, but I think most people here would really love F1. F1 is much more about technology than anything else. I love it.