Since the Xbox is basically a computer, including a hard drive, and it already has the ability to receive Foxtel over the internet, you could run a Foxtel IQ app (that is, a DVR) to record and rewind shows just like the dedicated Foxtel IQ appliance. The real difficulty, I expect, would be hard drive space, which is quite limited on the Xbox.
Mokalus of Borg
PS - You'd also have to convince Foxtel to go for the scheme.
PPS - Which I doubt they would.