We don't know much else, but we can speculate:
-Is Sega making an iPhone game? "Ringo" = "Apple" in Japanese. "Project Apple" could be a game for the iPhone we've ever heard of or seen. You'll presumably play it 24 hours a day, 7 days a week and undoubtedly be picking apples.
-Will "Project RINGO" finally unveil Sonic the Hedgehog creator Yuji Naka's platformer from Sega subsidiary (and Naka's company) Prope? Speaking with Gamasutra at last year's Tokyo Game Show, Naka said, "At Prope, we're actually actually planning on making a game like Sonic right now." That was four months ago.
-Is Sega making a game about NiGHTS and Sonic having a child who juggles apples and likes club music? Clearly the most likely choice.
Join in the speculation fun yourself in the comments!