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How about putting a receiver on tracking devices,

You mean like this, which is essentially long-range RFID?

Hey, if you have a lot of wanderers in your family, check out Project Lifesaver.

They have a wrist-mounted transmitter that lets police and caregivers (who have the receivers) find wandering patients quickly and safely. 100% success rate.

I definitely will, thanks a lot.

I wrote the code for the transmitters; it was done so well that they didn't need me anymore. (They got Microchip to program them by the reel.)

Same thing happened to me at one of my old sysadmin jobs; they hired me because the last guy couldn't distinguish telephony (or anything else, for that matter) from his own ass, but as soon as I had everything running ship-shape, they sent me down the road.

Lesson learned, for sure.

Hey, if you have a lot of wanderers in your family, check out Project Lifesaver.

They have a wrist-mounted transmitter that lets police and caregivers (who have the receivers) find wandering patients quickly and safely. 100% success rate.

I wrote the code for the transmitters; it was done so well that they didn't need me anymore. (They got Microchip to program them by the reel.)

I can imagine that autistic kids would be less likely to ignore a piece of hardware strapped to them.

It would be difficult/impossible to ignore, so a different strategy is in order.

My credentials:

My autistic son has something similar - http://www.projectlifesaver.org/ - and the trick was to get him to look forward to having it on. A week or so before we received the bracelet, we started talking about how he was getting a special watch. He shows it off to basically anybody who will talk to him now, which may be a bit annoying, but is worth the peace of mind should he ever wander off.

I wrote the code for the Project LIfesaver transmitters. They help people who have wandered away from care. THe average response time is within 30 minutes. (The alternative is to be found later, usually after dying of exposure.)

It has saved thousands of lives.

There's not really much benefit. The major upside is that you can't ever forget your wallet, and it's going to be a bitch to steal your card. (If the guy in front of you is trying to pay with a stump, then it's probably stolen.)

However, electronic tracking of people does have its place. (I wrote the code for those transmitters.) Some people will wander away and be unable to ask for help or even realize that they are dying of exposure.

I did a bunch of work for a dot-com startup in the early 2000s focusing on vehicle-tracking applications. I have a daughter with Down syndrome; Downs kids tend to wander too, so we looked at this issue quite hard. The good news: the technology is pretty straightforward. The bad news: that's about the only good news.

Batteries
A GPS chipset enables a controller embedded in the shoes (or on a device strapped to the person) to know where it is. The second half of the problem is to transmit your location to somebody else. The simplest and cheapest approach is sending the data via the cell phone system--eight years ago we were using the digital control channels of the AMPS (analog) cell system; today you'd use G3. But think of the problems you have keeping your cell phone charged--how often would you recharge the batteries in your patient's (or your child's) shoes?

GPS
GPS is a really cool technology--but it is frequently viewed as the high-tech cure for what ails ya. It is not perfect. In particular, GPS depends upon an extremely weak signal--the GPS chipsets use DSPs to dig the signal out of the ether. GPS chipsets lose "lock" all the time. If the patient is wandering around outside in plain sight, his GPS coordinates are going to be accurate. But when the chipset loses "lock" on the satellites, tracking devices will continue to report the last known good position. This can be disastrous: the patient wanders from a nursing facility out onto the public street--and gets on a bus. Inside that nice, big aluminum box he can ride all the way downtown--and his GPS-enabled sneakers will continue to report that he's out in the nursing home parking lot.

There's a serious challenge to solving problems with technology--you also have to make sure that the people who depend upon that technology know (and act on the knowledge) that it must be maintained, or it will fail. Consider, for just a moment, how many people die of smoke inhalation every year even though they have smoke detectors in their homes. But they didn't change the batteries....

There's a much smarter solution
As I mentioned above, I looked at this issue long and hard with a dot-com startup eight years ago. As we looked at it, we found a substantially better solution than GPS. Project Lifesaver is a not-for-profit organization started in Chesapeake, Virginia that has developed a simple, effective solution targeted at Alzheimers patients, Downs kids, and other "wanderers." The patient has a small bracelet (like a hospital bracelet) attached to his or her wrist: once per minute the bracelet broadcasts a serial value on a digital (i.e. low-power) frequency. If/when a patient goes missing, the people responsible for the patient call the police or the sheriff's office. The cops arrive with two directional antennas tuned to the frequency: they go off in different directions, do a little bit of trigonometry, and Grandpa is back in the facility in less than ten minutes.

The Project Lifesaver solution is not perfect. They have the same battery issue that the "GPS sneakers" approach has (the GPS sneakers approach has been tried again, and again, and again). They also will only work with local law enforcement agencies--in our county the @##$%#^^# sheriff cannot be bothered. They have had a lot of success with local service clubs funding the cost of the bracelets, and (more important) paying for and replacing the batteries.

The GPS sneakers thing sounds like cool technology. Using differential antennas and good ol' trig is much more effective. My daughter still wanders off occasionally (and we live adjacent to a state park)--I wish we could take advantage of the Project Lifesaver program here.

> but for the life of me I can't remember what the watch was called.

Project Lifesaver ?