Dungeon Defenders is perhaps the most visible Unreal Engine 3-powered game on the mobile OS, though a recent deal between Epic and Gameloft ensures that won't be the case for long. Companies can currently license UE3 code to develop Android games, though Epic VP Mark Rein told Gamasutra that "UDK is a totally different story."
"It'd be difficult for anybody right now to make a game with UDK and ship it on Android, because Unreal is for making high-end, high-quality-content games," Rein said, adding, "most of them are pretty large, because you can make a large game with it." Thus, Google's current 50mb limit for apps is kind of a problem, though it's one Epic and Google are looking to resolve.
"UDK will come eventually to Android, and Google is going to solve that problem," Rein assured. "We know they're working on it, but we don't know the release date and we don't know when it will get into the hands of all the different vendors with all the different phones."