Ok I confess, I have been trying to kill my iPhone 4 with my Sith death grip that is worthy of Darth Vader.

I did 2 experiments just make sure that it is repeatable. I held it so tight that could literally choke some small animal to death. You can see that the iPhone signal did drop but not so much that it completely render the phone useless.

Here are the videos

Part 1 of the Experiment

Part 2 of the Experiment