I, for one, am very eager to find out what IR pass filter is being used. My homemade headtracker works very well (also with OpenTrack, and PS3eye camera with IR block filter removed), except at a certain time of year and day when the sun shines into the FOV of the camera (and my blinds let through streaks of light). I was not able to find an affordable IR pass filter, as OP said right at the beginning of this thread, floppy and film don't work all that well (block too much IR and don't block enough visible light). OP said he could get 780nm IR pass filters for free in unlimited quantities... I'd settle for $2 for a single one :)
My headtracking cap is also wireless, the batteries have so far lasted over 60 hours, and according to calculations they should last over 120 hours. If I change the resistor to make the LEDs brighter, it somewhat improves the performance when sun is shining on me (after changing detection threshold in OpenTrack), but of course will reduce the battery life. I could maybe make another switch to change between bright and non-bright, but it starts becoming a clunky hack then (well, even more of a clunky hack than it is now).
A good IR pass filter such as OP describes sounds like an ideal solution... but where to get it?