I have seen threads here on building an ir tracker and several online. One used the ps3 eye cam with removing the ir filter. Years ago some folks were toying with vr displays using a wii mote as the ir camera. The VR monitor was a regular display that used a wii mote to track 2 ir leds attached to glasses to track head movement. I imagine this was likely what trackir & the other flavours was based/inspired by.
Here is a link to one of the topics here