An acquaintance of mine, along with her fiance and the pilot, were killed last year on a small aircraft flight through the Rocky Mountains. The aircraft ELT didn't go off, so their deaths were not confirmed until over a month later, when by a fluke, a local hang-glider pilot happened to spot the wreckage from the air.

I got to wondering, if I'd been aboard that aircraft and realised, too late, that the pilot was an idiot. (He had only flown that route once or twice before, and he took off between two frontal systems, meaning he had bad weather in front and bad weather closing in behind; stupid enough anywhere in the world, it was downright suicidal when trying to follow a highway through a mountain pass.) If I had a PLB, when would I activate it so that the rescuers would at least have a decent shot of finding my body? Would I just activate it for the duration of the flight, and turn it off and apologise to the authorities when/if we landed safely? Or would I have it clutched in my hot little hand, my finger on the trigger, ready to activate it as soon as a crash landing was imminent?

What if I was the pilot, and I blundered into a "Toto I don't think we're in Kansas anymore" type scenario? Now I've got my hands full flying the plane; should I just activate the device and forget about it?

Ideally, what I'd like to have is a timer switch that will activate the PLB in, say, 30 minutes unless I reset it (preferably with a nice, loud, annoying beeping sound for 5 minutes before it goes off). I'm inclined to doubt that any commercial PLB currently has such a feature. Am I wrong?

What are the pros and cons of such a mechanism?