Hi, just read the clock thread and it reminded me to mention this I found on the net. It's a tracking device mainly for kids but can't see why it could not be used with AZ sufferers. The wandering person would need to have the mobile on them on their travels and there wherabouts can be monitored on a laptop.
Here's the link
http://appshopper.com/lifestyle/family-tracker
Here's the link
http://appshopper.com/lifestyle/family-tracker