I just used an InReach for the first time. Basically, it allows you to send and receive texts anywhere in the world. It uses satellites (a.k.a. magic) and is fairly easy to set up. It's $264 clams plus a month-to-month or annual contract of about $25.00. But it works. Supposedly, you can send SOS messages but haven't had the pleasure of using that feature yet.
Even cooler and a lot cheaper: a kite. Ideally, a pegasus/unicorn kite. Why, you ask? Because it's light (.2 ounces), cheap,, and turns the top of any mountaintop hike into a dreamy, memorable moment or what Wordsworth called "a spot in time."