Yes, you need to subscribe to GameCenter Live. I did so through the GameCenter Live web site, and not through the app, as the direct purchase gives you the option to pay $20 monthly instead of $160 in one payment. Once you've purchased your subscription, you go to the settings of the app and entire your log-in information, and the live game feeds then show up. Keep in mind that it is still subject to regional and national TV related black-outs.
When are we going to get PPV single game options for sports??!! I'll never drop $150-200 on a season subscription for any league, but I WILL happily pay $3-5 for a live stream of a single Wings or Tigers game. I don't have time to watch enough to make it worth it, but every now and again I can get a sitter and a six pack and it would be nice to watch the game at home (no cable TV).