Well, considering Freetrack headtracking for a low-cost project, I would not spend above 20$ for high-tech filters. I tried out the most solution given here and they mostly works fine.
Floppy disk - good, but depends a lot on webcam.
Exposed film - good
Sheets of color plastic films - need some experimentation, but give some good results.
I finished with a Ir-filter from a Ir-receiver found on the front display of an old VHS recorder. Works like a charm.
Better spend that 20$ for a Freetrack-donation.
The led light is very visible so I dont think the ir-filter on the PS3 Eye is is very strong,
Yes, mostly they works fine without breaking the filter.