There were a couple of phones HTC made (both under their name and rebadged as early Google Pixel phones) that could detect squeezing the phone as a programmable button press. It seems like it'd be clunky and triggering at the wrong time or not triggering reliably when you needed it but it was just really well implemented so it worked perfectly. Slightly increasing how tightly you're holding the phone is such a tiny thing to do so getting a full extra programmable button out of it was actually really useful for making your day to day phone usage slightly smoother and more efficient.
I'm guessing it just didn't get enough use because people aren't likely to try it intuitively.