What to look for
Check what actually happens when the SOS button is pressed. Better units call through a list of contacts in order until someone answers, rather than sending one message and stopping. Two-way calling matters as well. Being able to speak is worth far more than a location pin when something has gone wrong.
Battery life should be measured in days rather than hours for anything carried daily, and the device needs to be small enough that it is actually on the person rather than in a bag left elsewhere.
Related
For older relatives, see GPS trackers for elderly, which add fall detection. For children, see GPS trackers for kids.
Common questions
Who gets the alert? Contacts you set in the app, in the order you choose.
Does it work anywhere? Anywhere with mobile coverage. It cannot report from a dead zone.