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.
Scott: Hey, can you believe Germany lost?
Me:Omg, I was about to text you the same thing! Talk about Text Telepathy!
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.
girl 1: I got this text message from Charlie which didn't make any sense. He told me to meet him at the molies.
girl 2: Well how did you figure out what he was trying to say?
girl 1: I used my text telepathy and figured he meant to meet him at the movies.