Both my truck and my wifes SUV have chipped keys. I had a non chipped key cut for each vehicle and wired inside of the frame rail on the passengers side of the vehicle. If the keys are locked inside (as has been done on a couple occasions) the non-chipped key allows access to the interior of the vehicle.

I also have hidden a chipped key in the vehicle compartment of the vehicle in the event that a key is lost. The non-chipped key is used to gain access to the vehicle and then the chipped key is retrieved to operate the vehicle. I hide the chipped key behind the glove box so someone would have to know where to look and then disassemble the glove box to retrieve the key. This way, even if someone finds the key wired to the frame, they could take the contents of the vehicle but not take the vehicle.

They'd have to be lucky to find the nonn-chipped key and extremely lucky to find both.

I also have a house key hidden outside, but you gotta go into the backyard to get it and even then if is not obvious where it is.