Ugh... Profuse apologies for not reading the whole thread. Misunderstood what your post was saying. Yeah, hopefully it'll be optional.
I've never hooked up multiple tracking sensors to a PC before. I've also never seen an option in any game ever to choose which head tracking device to use... Sounds like the time may come where that will need to be there.
Wiley.
there is a lot of software out there that will feed sensors into a compatible output (ie freetrack or trackir emulation).
Most of the time I use OpenTrack, there are other options such as OpenPIE and GlovePIE.
DirectInput also supports such devices, so if the game supports trackers via DirectInput you're also good.