The general theory that your mobile phone (cell phone) knows you better than anyone else based on hearing all of your phone calls, knowing all of your texts, facebook updates, emails, GPS locations, etc. and is therefore one of your best friends. After all, there is no person or device that you interact with more than your phone.
Dave and Hal are total cell mates. That guy takes his phone with him with everywhere he goes - even the different rooms in his apartment!
A witty and sarcastic way to describe beauty. Often used in its negative form (she ain't open casket material) meaning having (or not) a presentable look.
Look at that girl, she's open casket material. But her boyfriend I would close the casket on him.