I added some timing code to compute the video frame rate, the rate at which commands are being sent to the rover, and added a text display of the rover's current signal strength.
The control protocol is very simple. The client sends a string of commands, and the rover replies with a string of sensor values. Currently this only contains an integer representing signal strength, but will eventually include voltages from the IOIO, GPS data from the phone, orientation information from the accelerometers, etc.
Here's a quick snapshot of my little client program in action. Next step is to figure out how to use PWM on the IOIO board to control the rover's motor speed.