I agree it's far from perfect. I scared my wife pretty bad on a recent 7 day solo trip. I told her I'd check in at least once a day, and I actually checked in 2 to 3 times each day. It worked most of the time, except for 48 hours where she heard nothing. She thought I was eaten by a bear.
I'm trying to find a statistical "guarantee" that it will work. Like if it fails on average 1 out of 4 times, I could check in 4 times a day.
For the computer geeks out there, I believe the messaging works more like UDP than TCP. There's no check to ensure the message got through. And given the packet loss when bouncing a message off a satellite there's bound to be failures. I hope this technology improves.