SOS device for dad

My dad is 65 and still loves hiking in the desert with no cell signal. He's in pretty good health but usually alone I want him to have some kind of SOS device in case something happens.

He's always in areas he knows and has never been lost.

He usually only does day trips.

I was looking at the garmin inreach but I don't want to burden him with a monthly subscription (fixed income, tight finances) and he wouldn't be comfortable with us paying that for him. He also doesn't need to text we just want the emergency feature.

Is there something that might work better for just the SOS feature?