Sounds like nonsense to me. Can you cite references for all these things?

My suggestions are:

1) If you have faint or intermittent signals use text messaging.
2) If you have faint or intermittent signals keep your phone turned off to save battery life.
3) Always tell someone where you are going and what time they should expect you there (or back).

The reason for (1) is that text messaging uses less bandwidth than voice, and can be sent in a short time (i.e. can make the most of windows of opportunity as the signal becomes available). The reason for (2) is because if the cellphone cannot contact a cell tower it will keep increasing its transmit power in an attempt to do so. If there are no cell towers then it will be using full power to no avail. I suggest you keep your phone off but have a schedule- say every hour. This leads on to (3). The reason for (3) is "D'uh!". Not only can this person who knows your travel plans initiate help if you don't show up, but they will also know that you will be checking your cellphone only every hour to save batteries. Maybe you have an FRS or ham radio too, which should be turned off except for regular schedules to save power.

Or rather, that's my opinion.

A