In answer to your previous question, I have transmitted 3 times from my home (tests...determining button holding length, seeing how long to receive "okay messages", etc), 5 times from my vehicle while driving (the unit sitting on my passenger seat, mostly in Portland metro, but also twice in the gorge on 84), from high bridge on Eagle Creek, from Tunnel Falls on Eagle Creek, from the summit of saddle mountain, from the Grouse Trailhead of Silver Star Mountain, from the summit of Hamilton Mountain, from my place of work in Clackamas, from Mount Hebo, from Angel's Rest and from Devil's rest.
Obviously, these are all just my personal tests to see if I liked the unit for use over the summer when I plan on a couple of PCT sections and more than a few solo overnights. Each one went through no problem (although I realize that I wasn't exactly in any deep canyons). As stated in the link provided by RobFromRedland, each time I probably had a bit more patience than some of the testers, and three of those times I was on a cell phone with someone seeing how long it took them to get the message...each time was 5-10 full minutes.
I don't own stock in this thing BTW, and I am much less interested in its life saving capapbilities than its communication. I just think that for what it DOES do and the price point it comes in at, it doesn't deserve some of the negativity that it has received.
I'll be keeping mine! 
-aaron
"Nature does not hurry, yet everything is accomplished." -Lao Tzu