Tom is looking for a GPS watch that has cellular service, which can be worn by a sleep walking child. They need to have a lockable wrist band so he can't take it off. Leo suggests several GPS watches out there, but none with a lockable watch band. Leo recently got the Samsung Gear S3 Frontier. It has all the features Tom is looking for, as well as a 22mm removable band that can be replaced. You can also make calls to and from it. The battery life is on long side for a smart watch.. MSRP for $350. It is compatible with Android or iOS. Check out AutismSpeaks.org. They have location devices that could be well suited for your needs.
How about a webcam that takes time lapses? Leo says that all of them can do that with the right software. ChronoLapse is a good application for that.