I will post pictures of my tomtom hardwired and flush mounted to the silver panel to the left of the steering wheel - great location, super clean and unless you get right up to the car you won't see it in there (the temptation to steal a $199 nav unit is beyond me, but you gotta get yo' meth somehow, I suppose)
IMPORTANT: Some of these nav units aren't 12v, so if you hardwire them by removing the cigarette lighter plug, you might smoke them. I learned that the hard way. Fortunately it was replaced under warranty. If you are going to hardwire them, you should leave the cig plug and just mount it into an add a socket, tape it up so it won't ground out, then hardwire the add a socket.
IMPORTANT: Some of these nav units aren't 12v, so if you hardwire them by removing the cigarette lighter plug, you might smoke them. I learned that the hard way. Fortunately it was replaced under warranty. If you are going to hardwire them, you should leave the cig plug and just mount it into an add a socket, tape it up so it won't ground out, then hardwire the add a socket.