It's not always possible, but a cell phone should only be used to effecitvely communicate that you are injured and where you are. You should possess the self-knowledge and skill to save your own butt. Do not rely on others to come save you.

Yes, I realize there are other things like stroke's, heart attacks, and other accidents, or simply caught unprepared, and immediate help is needed and you could die in a matter of minutes. If this is the case, then, well, you're going to need more than a cell phone on your side.

Always know where you are. I have to admit, I don't always do this, and have realized if something happened, I have no effective way to locate myself within miles. Pay attention when you are travelling in unfamiliar area.