its Skype integration and the soon to be imported GPS functionality. However, a story from a Michigan middle school recently broke the news of a heretofore unannounced ability of the PSP -- instantaneous superheating, with possible leg disfigurement.
Apparently, a student had the system turned off and in his pocket in the middle of band practice when, all of a sudden, it melted through his jean pocket, sending him to the hospital with second-degree burns on his leg. Sony has yet to comment on the incident, though their website reminds PSP owners that using third-party batteries and charging equipment is likely to cause such an accident -- as will playing the trombone within a 5 foot radius of the system, apparently.
In a beautiful showing of coincidence, the game occupying the system at the time of the meltdown supposedly was, you guessed it, Burnout Dominator.