During Sony's press conference, the company announced a cross-platform action RPG titled Ruin, coming to both PlayStation 3 and PlayStation Vita. The game was touted as a fully featured RPG, with a focus on attacking opponents' lairs and protecting your own. Being constantly connected means attacks happen in real time, so you get more experience for protecting your lair as it's actually attacked -- a not-too-subtle way to encourage you to keep your Vita with you.
On top of that, Vita will let you pick up your progress between the two platforms. Using cloud saves, you can freely transfer from your PS Vita to your PS3, and vice-versa. This is similar to the "Transfarring" feature announced by Metal Gear Solid creator Hideo Kojima a few days ago.
The conference is still ongoing. Shacknews will update with more details as they become available.