Here's one approach re: stealth from Kevin Kelly's excellent Cool Tools blog:
My Jeep is camouflaged to look like a commercial fleet vehicle. I made up a fake company name, appropriated a 1950s-era logo that once belonged to a nuclear energy mutual fund, painted safety stripes on the back, and plastered a fake vehicle number all over the place. I also added flashing yellow lights in the rear window, and a police-style spotlight and rubberized push bumper to the front. VERY FUN accessories ... and useful too (when used with discretion). The spotlight is incredibly versatile -- you can point/rotate it while sitting in the driver's seat -- and it's come in handy countless times for roadside emergencies, setting up campsites, or finding house numbers on dark streets.
This urban camouflage guise is very useful for parking in yellow zones, urban/industrial exploration, and crime deterrence. And the thing is... it really works!