Georgesgran
Probably a bit of both. Genuine and it would be expensive and if a scam, they’d ask for your bank details.
However, these alarms which are either worn around the wrist or as a pendant are freely available - one from Age Concern is £25.
Don’t know where you got your information from, but you are wrong to just say the One from Age Concern is just £25. A personal alarm has a monthly fee, not a one off fee.
Vulnerable people (not just pensioners) also have to have responders, either family/friends/local support groups or pay to have a care company to respond, so very much more expensive than a one off £25.