Blizzplanet has uncovered that Blizzard has apparently filed a patent for something called "BattleChat," which purports to provide "an interface for the electronic transmission of messages and data including voice, text, and message transmission." Along with the recent news that Blizzard is seeking mobile developers, Blizzplanet supposed that this means Blizz is developing a mobile application for chatting with players either in World of Warcraft or Battle.net (their online network from previous games).
It's all speculation at this point, however-- we did hear back at BlizzCon that Blizzard was planning some really interesting updates for Battle.net, so this just could be a social networking launcher/application for Blizzard's games (chat with, and play with, your friends in multiple Blizzard games at the same time). Either way, odds are Blizzard is working on something big.
And Blizzplanet also discovered that Blizzard also recently updated their Blackthorne patent as well. So if anything is going mobile, that's another good guess (seeing as the game has already been released for a few older consoles and the Game Boy Advance). If these patents are any indication, there's going to be a lot of interesting products on tap at Blizzard Entertainment.