There's a commercial company called Zoomsafer that has been doing work related to this. Their current software offerings focus on measuring use of devices in fleet contexts to help companies manage risk.

You could use the TAPR Open Hardware License:

http://www.tapr.org/OHL

It's a copyleft-style license drafted by a lawyer that permits a broad range of activity. Bruce Perens and Eric S. Raymond helped review it. Open hardware licenses are still in the early stages of evolution and adoption. If TAPR does not meet your needs, the Wikipedia entry on Open-source hardware lists more alternatives:

http://en.wikipedia.org/wiki/Open-source_hardware