I have seen a thread about changing the rpm lines on a MINI to do exactly what you are talking about. They had to hack into the CAN Bus and modify some of the internals to drive the led's properly. I think the write-up was on
www.northamericanmotoring.com. Do a search and it should pop up.
Edit: Found the thread, good luck.
http://www.northamericanmotoring.com...le+shift+light