To what technology of iPhone are we refering here? None of the iPhones I have used has been able to identify whether I am unlocking it with my finger, toe, nose or side of my palm. Obviously not counting the new fingerprint technology where I can only choose one of this to be used.

But anyways, I also think this would be cool feature to have. On personal usage I would agree with Pichlo, I would be too afraid to have it on since I often do have my hands tucked to same pockets I might have my phone in.