And of course.....

"A new application from SCE called "PlayStation®App" will enable iPhone, iPad, and Android based smartphones and tablets to become second screens. Once installed on these devices, users can, for example, see maps on their second screens when playing an adventure game, purchase PS4 games while away from home and download it directly to the console at home, or remotely watch other gamers playing on their devices."

There are several demo videos online. I found this one pretty interesting.

Via: http://technabob.com/blog/2013/02/20/sony-ps4-specs-games-announced/