This is pretty cool, as it plugs into your OBD2 port.
http://www.plxdevices.com/products/dm100obd/
Someone buy it and give me a call so I can come check it out.

 

I think this thing can read DTCs as well.

 

I've been contemplating this for a while since you posted. It's very interesting.

 

I think you need to be careful which one you buy because there's an OBD2 version which acts like a scanmaster, and then there's just the generic gauge that hooks up to other units. This could conceivably go into Sue's car very easily as well. It just hooks up to the OBD2 port

I may get the OBD2 version as it'll be like having a live logger in a gauge. It should read boost up 18psi (the SSM protocol only reads up to 18.4) as well, and you can add modules so that it can read oil pressure, lambda etc..