The basic idea is that connectors on electronic devices are often used in unexpected ways and that some devices, especially phones and tablets, even multiplex several functions onto a single connector. We demonstrated how we are able to access an interactive shell on certain Android phones by connecting a special serial adapter to the phone's USB port; although we were physically connected to the phone via the USB port, we were not using USB.
Similar multiplexed interfaces are present on a wide variety of portable devices, often accessible via USB or headphone connectors. An excellent example using a headphone jack was published earlier this year. We hope that our talk will raise awareness about the attack surfaces presented by these types of interfaces.
The talk at ToorCon was a lot of fun. We got a shell and activated adb on a phone handed to us by a volunteer from the audience. I hope you enjoy the video, but you should also read the paper we wrote for Black Hat.
We've posted links to several resources related to the talk.