The Vello I have is RF, not IR, so you don't need line of sight. I've tested it with the camera in the backyard and me 150' away on the other side of the house and it worked fine. And it does register the half-press to focus.
I also have the ML-L3 IR remote as well, and love being able to just stick it in my pocket in case I need it while I'm out, but it won't work with the D800, and you need line of sight. The Vello came with 2 cables, one for the 10-pin and one for the USB jack. Sorry if I confused you.