I'm looking for advice on buying a 'medical alert system'

I'm 71, live alone, and have health issues.

I'm thinking of getting one of those medical alert systems where I can push a button worn on a cord or wrist device if I need to signal help.

I don't have a landline, nor want to pay for one just for this, so am looking at something that works off my smart phone, wifi, etc.

Any info, suggestions, experiences would be much appreciated.


Thanks