Positioning system - Animal movements

[ADAPTH]

Hello,
I am searching for a system that could help me to find somebody. I am
occupational therapist and one of my patient want to go away with 
his wheelchair. The problem is that he has sometimes problems to find his 
way back.

So I would like to find a device that could give (without speaking with
him) me his position or that could help me, in a way or another, to find
him.

We have posted this message in other newsgroups and we receive the
suggestion below. 
"Biologists studying wild animal movements in this country commonly use
"radio collars" or small radio transmitters implanted in the animal. These
radio transmitters send out a signal constantly that can be picked up by
two receivers, and the signal can be tracked that way. If you were here, I
could borrow the various bits required and we could experiment to see if it
would work for your client. 

There are also "radio distress beacons" that can be gotten here, and, when
activated, send out a signal that causes a search and rescue operation to
be started. They're meant for things like plane crashes, but the technology
is pretty simple. Could your client operate a push button or a pull chain
if she or he were lost?"


It is the reason why I ask you if this kind of system could be use by a
human people (wrist radio collar). Could you tell me where is it possible
to find a commercial retailer in Luxembourg or in Belgium, France or
Germany.

Thanking you in advance

France ROLLAND