Well, we just purchased a secure keybox and mounted it outside by the door. It has a cylinder lock with a 4-digit code that can easily be changed. When Tom wasn't able to get up and someone had to get in, they called him and he just gave them the code so could they open the box and use the key. Then they just let themselves out, put the key back in the box, and spun the cylinder. If it's someone he doesn't want to have access again, he changes the code as soon as he is able.
I found his keybox at Home Depot; sorry, I don't know your location so I don't know what store to recommend.
If you want something more hi-tech, try smarthome.com. I found a number of systems that work independently or with X-10 technology.
http://www.smarthome...CFRSdnAodu0OUrQ
Hope this helps - you sound like you already know a lot about these systems so I hope what I offered wasn't too elementary.
Edited by hooplady, 10 December 2009 - 07:14 PM.