Pollie Barden Networked Journal Project
I was wrong about the sensor. It is an analog QPROX (proximity sensor) that is constantly on using PWM (pulse width modulator: technique for controlling analog circuits with a processor's digital outputs). I think she's going to ground the cover of her book with some conductive fabric. I really can't wait to see this at ITP show.
For more information about Pollie's work, click here. She also designed and produced this cool laptop tray for one of the kids in her assistive tech class. I think he was very happy with it.