Touch Arcade has word that one of 2008's best iPhone games (our 2009 list is coming out this week), Fieldrunners [iTunes link, $2.99], has released an update (1.3), in which they've released two new maps available as in-app purchases, and they've included OpenFeint 2.4 functionality, with messaging, chat, and everything else the in-game social network portends.
The two new maps are called Skyway and Frostbite. Skyway boasts a metal floor with a few holes in it, which limit where you can place your units in the tower defense classic. Frostbite is a snowfield with a base in the middle to defend from attackers on all sides. Seems like both offer up some interesting twists on the gameplay -- they're 99 cents each (a fact that has the most recent iTunes reviews up in arms), but if you ask us, two bucks for new content is cheap, especially if you're a big Fieldrunners fan already.
The update itself is a free download for paid users, though, so if you want that OpenFeint functionality, hit up the App Store and load the game up yet again.