I've searched online for an answer, but I haven't been able to uncover much information. If Windows Vista is installed as a guest OS, would it be able to detect and use a tv tuner PCI express card that is installed on the physical host?
As Hyper-V is intended primarily for server consolidation I doubt it would be supported. I haven't had reason to test this specific scenario myself but my answer would be no.
I have to say i've not come across anything in the options that might let you do that... The main kind of hardware passthough i have seen is primarily storage controllers.