For starters most video staking apps probably won't allow you to use 3G (although I may be mistaken) due to the bandwidth needed to do said streaming. If your cable provider has its own app, but you don't like it, you probably won't find another option as I presume you pay for your cable service and you would therefore need to prove you do pay by logging in before using their app? For this reason a third party app that shows the cable shows you want probably doesn't exist as they wouldn't be able to get the rights to provide the channels. Sorry to be the bearer of bad news. I coul dbe wrong, and if so I look forward to seeing the answer, but unfortunately I doubt there is one, sorry.
Proud owner of a 32GB wifi iPad2 iOS5.