The Workshop

Here's a fun little project that makes you, if not invisible, at least unrecognizable on the IR-favoring security cameras after dark.
Note the person in the right-hand picture who appears to have a blinding light on his head. Now if you're that worried about being identified after dark, you may be a high-ranking politician, or some other kind of miscreant, but down in the comments, there's this:

I though about something along this line for license plates. Since the cameras that shoot the plates are tilted towards IR (like the security cameras) you should be able to over expose the shot making it so the letters cannot be read using electronic means but perfectly readable by human eyes.

Indeed, the thing may well work better after dark, but there's an interesting experiment to be tried here, A license plate frame surrounded by IR LEDs would not be noticeable under ordinary circumstances at all. The LEDs would be on all the time, of course. Perhaps testing could be done with an ordinary digital camera, I don't know. Someone with a CNC mill and a slab of PVC could knock out a couple frames in short enough order.