Suggestions for emergency alert

My 95yo mom lives alone in her house, a few miles from me. I’m trying to find an emergency alert system and what I’ve found thus far seem to need a home base or cell phone to be tied to. This doesn’t work for my primary concerns. Looking for recs for something that meets the following criteria:

1) must be a standalone system, not tied to cell phone which she doesn’t have.

2) must work away from the house. Gardening and walks are the most likely times something will happen.

3) does not require her to hear or have a conversation. Not happening; her hearing loss is extreme on a good day, worse when under stress.

4) I’m the primary contact, not 911.

I just want to get an alert. I can get there quickly 99% of the time and I’ll know where to find her if she’s not in the house.

If anyone has suggestions, I’d appreciate it.