ReplayTV DVRs used to have that, but they removed it from their later shipments (I have one of each version). I think DirectTV bought out their patents, but I haven't heard of them using that. The satellite companies want to stay on the good side of the broadcasters so probably wouldn't put that function on their DVRs.
IIRC, the broadcasters took heat from advertisers and the crap rolled down to the electronics makers. They removed the commercial zappers or anything close.