I was browsing, strangely enough for CNC stuff and ran across this.  It's a very lightweight modular camper kit system and it looks like you can customize for whatever size trailer or pickup bed you want.  You could even use it for a ground-based shelter.

http://www.youtube.com/watch?v.....Z3ymYlWX8#!
http://tealcamper.com
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Seems a pricey for the size, considering you also have to purchase the trailer, but you do have a hard-sided trailer when you're done.  I think a one good use might people building toyhaulers on flatbeds.

You'd definitely get some looks driving down the road.  It doesn't look like any other camper I've ever seen.