Lots of good ideas already. Here are a few more:
1. 2 meter ham radio. These can get out a long way. Once while in Moab there was a group that was late in returning. I was able to talk to Clint from about 45 miles away through canyons etc., so we didn't have to worry about them. That may have been a fluke, but they do have good range.
2. A SPOT. This is a satellite signal generator that has 3 different buttons: you can say you're OK; or you can signal you need help but no emergency; or you can signal 911 and they'll send all available resources. The SPOT gives them your exact location and with use of a hybrid map and photo, even show the trail you got there by. I've used a SPOT a lot for remote GPS work while working separately, but I'm always in touch with those that can help if needed. Normally about $150, some places are giving these away free with a subscription, which are less than $100 per year, I believe. Almost as good as having a satellite cell phone.
Lastly, there's the "Help, I've fallen and I can't get up" T shirt. This has NOT worked well for me - everyone just laughs.