Bluetooth Hack?

[Head Tax]

About a year ago my mate from school showed me this hack that he could do using the bluetooth on his phone. He searched using his bluetooth (on his Sony Ericsson) and connected to my phone (I didn't accept it or anything it just did it) he turned my phone of silent, and started playing through the songs on it in the middle of class Anyway, I asked him how he did it but he didn't tell me and said you had to have a Sony Ericsson to do it (I had an LG)

Well I got a Sony Ericsson in the summer and I was wondering if anyone could show me how to do it? I think it was just an app he ran from his phone, but it was done without me knowing at all, he had control of my phone and later on he phoned someone using my phone, and you could hear them talking on my phone, and his phone at the same time.

Just wondering if anyone knew how? Thanks!