The thing is, unless you can find something like TwoRails suggested, you're stuck with a problem:
Either your camera has to have software that will recognize the flash drive, and send pictures through, or the flash drive has to have software to interface with the camera and take pictures off of it.
Interesting idea, but I don't see any on the market as of yet. You never know, it might be here in a year!
Going further, the infrastructure needs to be improved. Most camera interface cables don't transmit power, that I am aware...