You guys have helped me out a bunch so I thought I'd post this and hopefully someone will find it useful. I had an external security keypad on my 2007 Escape Hybrid that (of course) died and there's no way to replace the battery -- although I tried, let's just say that cutting membranes with scalpels and shoe goo sealer lasted about 2 months. To replace the Ford keypad (which is just stuck on with decal tape) was a pile of dough but there was no information (that I could find) saying whether the newer (cheaper!) low-profile keypads would work with the older systems. So I just went for it and I'm happy to report it works fine:
http://www.partscheap.com/Ford_Escap...4a626-ba-1.htm

The added benefit is you get a whole new 5-digit security code so all the ex-family members and babysitters I've had to give it to over the years are now out of luck (I know, I could have programmed a throw away code but that's *way* too much preplanning for me .) Last but not least, I think you guys gave me the idea of putting the new keypad under my gas cap door, but I couldn't make it fit so I took off the housing (not required for waterproofness) and using foam doublesided tape put it above the gas cap (it's more secure than it looks.) So far so good.

 

I had a couple of keys cut at Home Depot to use for "lockout" purposes. They are for the door only and won't start the FEH. But they are cheap and smaller in size than the stock key since there's no plastic on the key. Might be another alternative to the keypad for some people.

 

Here's another thread that might be useful.