I recently saw this Hide-A-Key for sale on the web and just had to have it. It is made to look like a sprinkler head. You just plant it in the ground and your done. Every criminal out there knows to look under the mat, in the flower pot or in the fake rock for the keys to the house. This is a slightly better option in that when you place it in the ground it does not look out of place.
The top unscrews to reveal a rather sizable compartment for holding the keys. It comes with two clips to hold multiple keys.