Needing a small tracking device.......

Life alert?

If he got the Covid vaccine, he surely has a Bill Gates tracker inserted....

Try doing searches for tracker for autistic child. Angelsense.com is one. But I don't know what the pricing Etc is like

I love these!  Never looked them up because they seemed kinda lame but OMG!  Brilliant for wanderers!

You pair it to your phone through bluetooth.  It then uses the bluetooth network of other iphones and macs, just like the "Find My" app.

I think she should consider something more low tech. Put alarms on ALL the doors of the house. If he turned off his phone is he going to consent to hanging a GPS tracking device around his neck or one his wrist? Garmin makes GPS trackers for dogs but, they aren't small. There's also a subscription cost.

If he's out of cell phone coverage or he's turned it off. It's no use. Also, air tags use other phones. Is someone else going to be in the woods? Bluetooth has a very limited range.

I would never depend on cell phone coverage for a health and safety situation.

I wouldn't depend on him always carrying his phone. I also could not get Mother to wear a fall alert bracelet even before her dementia worsened. Her wandering was dangerous because she kept crossing the road. We did put better alarms on the doors but she still got pretty far before we could catch up to her. The last time was nearly dark, she was in her nightgown and no shoes. One time she tried to flag down a car and tell them there was a stranger in her house. Wandering can get very dangerous. Your friend needs to start thinking about what they are going to do if the behavior continues and worsens. At some point, she may have to call in the sheriff if she can't find him and I would think that may be the time that tough decisions have to be made.

In this situation, I'd look for a small tracking device that could be put on his shoes or something. I don't know of anything. I just know you can't count on them to carry something or to have the presence of mind to push a button like on a Life Alert type system. It's the beginning of a rough road, unfortunately.

A tile?
My husband has them on his wallet, keys, our dogs, and our tortoise. His phone has an app. He’s used it for the tortoise and his wallet. I don’t know the range, though.

Call a local Senior’s resource source and see if they have suggestions

I don’t think any tracking device is completely foolproof. Even when my mom was in a memory care nursing home she cut off the wrist trackers twice! They had to put it on her ankle so she would forget she had it on. If a person is starting to wander, it really is time for the caregiver to start thinking about getting help with some kind of full time care. It’s all really hard. I’m sorry your friend is going through that. 

I dont think a tracking device is foolproof enough. If he is prone to wandering, it may be time to consider another living arrangement for him.

My mom would throw her belongings in the trash. Wedding rings, phone, her clothes. I know she would have thrown a tracker away. Maybe figure a way to lock the door in a manner he can’t unlock quickly? Obviously that wouldn’t be ideal for a medical emergency situation though. It’s a difficult situation and I sure hope you can find a solution that works.