I guess every microwatt counts: MEMS environmental power.

[skids]

Not much environmental impact perse, but here's your modern equivalent of a self-winding wristwatch.

http://www.eetasia.com/ART_8800378146_765245_1fe14900_no.HTM

...though they did miss the MEMS heat engine angle, which is more efficient than current peltier effect materials. I'd say there's a race on but the MEMs stirling is pretty much ignored, while peltier materials are researched heavily and will be improving in strides in the coming years as clathrates are perfected.

http://technology.grc.nasa.gov/ssreadonly.asp?item=9

This stuff could be a valuable larger-scale electricity generation resource eventually -- like in a decade or two -- if large arrays are fabricated.

Oh there's also this:

http://www.eetuk.com/tech/news/rn/showArticle.jhtml?articleID=18309660