While probably better than relying on mobile towers, aren't satellite communications difficult with a dense forest canopy? Probably best that people be aware of the limits of their devices before heading out.
Likely the satphone is better, but there are still limits.
Why not? There are all kinds of Emergencies. Some trees are fairly easy to climb.
If your GPS can get a fix, you can probably find enough signal to send a SBD.
Iridium carrier signal is stronger than GPS.