When you are in the middle of texting someone and he/she texts you the exact same thing. Can also be used when IM'ing someone.

Someone people turn to when they're sad who makes them feel better.

Text telepathy is used when you receive a text message that is full of typo's or doesn't make sense. The receiver can usually figure out what the sender meant. Usually mistakes are made when texting because the keypad is too small, auto-fill kicks in, or simply because one's fingers are too big.