In an effort to record, review and share with parents a student's ability to use a high tech AAC device we recently mounted a Flip Camera to a students wheelchair. Currently we have about 45 minutes of footage which gives us an interesting perspective on this student, the device usage, the motor skills used in accessing the device and some of the linking between pages the student does with out actually "saying anything out loud" (this was surprising to us). As we set up the camera to show only the device screen and the users hands the footage catches things we miss when we think we are watching how the user is accessing the device. The footage is also great for calculating data points for alternative assessment and progress reports.
If you are supporting any high tech AAC users I would highly recommend trying this out!