Also known as 'laptop leg', this is when your foot and/or leg goes numb because of the way you are standing/sitting. Due to your avid interest in you device, however, you don't notice until it becomes painful.
Guy 1: Hey man, why are you rubbing your foot?
Guy 2: I was just standing by the kitchen counter looking at my phone, and suddenly my foot went numb.
Guy 1: Ah, another case of 'phone foot'.