In some wilderness areas you can, or even are encouraged to check in at a trailhead, either with a human or by signing in to a book. This is old-fashioned but reliable if used properly.
Wilderness accommodation may also be used to helping out here; even a fellow visitor in a hostel/mountain hut could be a suitable contact.
Certainly when I stay in a big ...
A simple, free solution here that should cover the bases.
Create a WhatsApp group with some people that you'd trust enough to keep track of it. Post in there when you're planning/leaving for a trip, your expected return date, and how often you'll "check-in".
Install the What Three Words app onto your phone and periodically share your location (and ...
If you genuinely have no one who you can use as an SAR contact you could purchase a either a GPS SPOT device or a PLB which can be used to emit an SOS signal that will be detected in an emergency even outside cellphone coverage areas.
Remember your SAR contact doesn’t need to be a friend. They can be a work colleague or a neighbour. You don’t even need to ...
Not a complete solution, but how about AllTrails lifeline feature:
If you're overdue messages go out. Unfortunately, I don't believe it can be set to only send an emergency message, nor am I aware of any other such solution that only sends the overdue message.