Fox is ahead of the curve:

News Corp.'s Fox Entertainment Group has worked a deal with its sister company DirecTV to offer shows on demand, but this arrangement is something different from what you've come to expect. The deal involves the FOX network as well as its cable/satellite FX channel, and will see the company offering on demand content not only following regular broadcasts, but users can pay a premium price to see content before it is aired. "Hit" Fox content such as 24 will be available after airing for 99 cents, but $2.99 pre-air episodes of FX shows The Shield, Rescue Me, It’s Always Sunny in Philadelphia, and others will be available also, typically 24-48 hours in advance.

I can definitely see the $2.99 being worthwhile for shows you really don't want to miss, and would rather not wait to see. If Sci-Fi channel were in on this, I'd definitely pop the surcharge to get an episode or two of BattleStar Galactica or Stargate before a vacation.