Here is a wikipedia article quoting of his experiments:
The first stage of this research, which began on 1998-08-24, involved a simple RFID transmitter being implanted beneath Warwick's skin, and used to control doors, lights, heaters, and other computer-controlled devices based on his proximity. The main purpose of this experiment was said to be to test the limits of what the body would accept, and how easy it would be to receive a meaningful signal from the chip.
The second stage involved a more complex neural interface which was designed and built especially for the experiment by Dr. Mark Gasson and his team at the University of Reading. This device was implanted on 2002-03-14, and interfaced directly into Warwick's nervous system. The electrode array inserted contained 100 electrodes, of which 25 could be accessed at any one time, whereas the median nerve which it monitored carries many times that number of signals. The experiment proved successful, and the signal produced was detailed enough that a robot arm developed by Warwick's colleague, Dr Peter Kyberd, was able to mimic the actions of Warwick's own arm.By means of the implant, Warwick's nervous system was connected onto the internet in Columbia University, New York. From there he was able to control the robot arm in the University of Reading and to obtain feedback from sensors in the finger tips. He also successfully connected ultrasonic sensors on a baseball cap and experienced a form of extra sensory input.