To clarify, here is what I did. I had a plain Jane second key cut. Tell them you want them to cut it from a brass blank. I put a little grease on it and hid it under my car with a twisty-tie. In the bottom of my center console, under all the "stuff", is my third spare (factory original) electronic key (button side down). When you lock your keys in the car away from home, unlock the door and start the car with the electronic key, and re-hide the hide-a-key. But, do not hide the key while in your driveway where the neighbors can watch you.
08 Liberty; 67 Jeep M725 ambulance;
04 Ram 2500 CTD; 46 Willys CJ2A (not currently running)