What's the best brand of pocket alarm

[UntilYourNextHairBrainedScheme]

Does anyone have a keychain or necklace or similar pocket alarm which either makes a loud noise or (and?) alerts a contact number (eg. parents/ partner) via your phone if you press it?

I'd like a recommendation for a teen who has to travel home not especially late but in the dark, and has a short walk on a road with a pavement but not many pedestrians then has to catch a train at a fairly small, station (so only a few people around, often a distance apart and no obvious staff).

There are lots of kwy chain alarms on online selling platforms like Amazon but obviously reviews are often manipulated/ bought, so I wondered if anyone has a recommendation for one they or their teen has?