While we've been using the term "personal computing" for well over 40 years, the device in your pocket is really the first computer-worthy of the moniker. Consider that the typical smartphone possesses the senses of vision, audition, mechanoreception, equilibrioception, and thermoception; and they’re all backed by information regarding the user's location, friends, schedule, correspondence, etc. Now, top it off with a full-time connection to the Internet. If we define context as the sum total of everything that the user is experiencing at the moment of engagement, then the mobile device has the unique ability to gather contextual information and provide relevant content in ways never before imagined.
(From David's Digital Atlanta 2012 presentation: http://digitalatlanta2012.sched.org/speaker/davidreeves1#.UJrw7GCD2oI)