Cellphones, at least they can work out roughly where you are from the base stations. But with satelite phones, they don't have that. So you could still call for help, but where to send help to?.....
But, with a good compass, you probably would not be needing to call for help.
Though modern GPS will work with supprisingly limited sky view. It's something we see in 'urban canyons'. Where the buildings either side are tall and you only see a strip of sky.It may just take a bit longer to get a fix. That may make a SPOT tracker a little more reliable, if you were out in the deep bondu.