I was 20+ miles away from my house the other day, and was still using my Portal (first time testing it that way). It worked great for me. Next week I am going to try when I am on vacation, and see how well it will work. I doubt it will be as good, due to hotel wifi, but worth the experiment. Slower, turn-based games, will probably work with no issue.
For the OP: you could not do that with WiiU. You were limited by the radio signal the WiiU transmitted. It was not over your network.