That's already available for anyone with a smart phone. It's a panic button AP, and you can give loved ones a "find my phone" connection to your phone to know exactly where the phone is. Literally the only difference is, it isn't strapped to your wrist. Maybe the new Apple watch has all these capabilities?
Anyway, there is nothing to keep a perp from cutting anything off you they want to, so whether it's in the form of a bracelet/locked ankle band or cell phone, you've already got all the technology available that you are wanting.
https://panicbutton.io/