The iPhone does not know enough. Proper context will require data in many more dimensions, dimensions which can define the user and his state. Their sheer number will placate strenuous constraints on their size and energy consumption but demand ever more accurate data. It is not difficult to realize that sensors will ride the next wave of innovation in computing. These minuscule and sophisticated apparatus will usher in the age of personal data.
Great post by Amit Jain.
More sensors and new algorithms will make our devices more personal, context-aware, and versatile. Let's keep in mind that, however, more always-on sensors will require Apple to make significant strides in another area.