I'm pretty sure the 8800 series does not have VIVO capability. You may see some third party designs way down the road that have VIVO but not currently.
on 7900 series, reference boards had traces for the required encoder chip, but none of the first boards out (in US at least) had the chip, hence no video-in capability. Eventually XFX (and now others probably) produced a board with the encoder chip and hence listed VIVO capability. NVidia lists VIVO capability for the 8800-series boards, but none of the ones available now (in US) have VIVO capability listed (presumably no encoder chip). I think in Europe, the Gainward Bliss 8800GTX has VIVO.
The 8800GTX does not have VIVO, you can tell from the lack of video in cable accessory you get with your card and at GeForce Lan 3, a friend and I talked with some of the gpu engineers and they said that the vivo functionality wasn't a sufficently demanded feature for them to put the chip necessary for that function.