You should be able to copy a vehicle key without the chip and use it for opening the door. It won't work in the ignition but if all you've done is locked the keys in the car it should do the job.

The other thing to do for this situation is to have one of those push button locks for the door and a spare key hidden INSIDE the vehicle.

Wish I had one when I locked my keys in the vehicle LAST weekend. It cost me $40 to a tow-truck operator to come out for 30 seconds of work!

I refound this website for a hitch receiver safe. Niffy but expensive. http://www.hitchsafe.com/