Sounds like we subscribe to the same school of thought on homeland security!
Yea more or less. My dad and I once built our own system though. A very basic and very reliable burgular alarm with a motor driven siren. We built it when I was about 14 years old out of some discarded relays he got from work.
The codes on my door aren't for the crooks benifit although it would make them stop and think LOL. It simply informs a cop, fireman, or parimedic, that in the event of a medical or fire emergency someone may be in the front bedroom and to do a welfare check. It's so they can get my wife out of the house. It also has two phone numbers one is my cell always with me. On the other hand if I had put up a wheelchair symbol outside that leaves her more vunerable. The codes only tell those who need to know what they need to know. Oh and she can single action a 38 SP I leave her with. When I'm home the 357's go back in. :>}