If you are thinking about a 12V DC onboard air system this looks like the way to go:


http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=11751&item=3810995689

Not bad it looks almost the same as the extreme air compressor.
It puts out 3.0 cfm@90 psi and 3.4 cfm@40 and is 100% duty cycle it has a 1.5 gal air tank also is 12V so you could wire it right in. It would be great for airing up tires you can supposedly run 3/8 air tools with it. It goes for $179.99 they have a direct phone # 800-821-2932
I personally would pull it from the 1.5 gal tank then weld on a custom bracket and mount it to a 7 gal air tank myself.


Anyways some food for thought.