i know the track IR has gone down a bit since they first came out.. but, for the TRUE cheapskate... this may be the salutation!
http://www.edtracker.org.uk/
this website has the program and the tech schematics to build a USB Gyro system with accelerometers. no need for a detection unit or a reflective thing on a hat or glasses. all for around 30 bucks?
this site also has a link to even a cheaper alternative. it can use a infra red LED or even a regular LED and a webcam.
there was another one i didnt look at. it seemed rather cool though.
enjoy!
