The Apple case has some ‘smarts’ to justify its name. For starters, it includes iOS system integration to show the battery pack status in Notification Center and the lock screen. The case itself also includes a discreet light that indicates charging status (amber, green, or off).
Moreover, Apple says that other cases often impair cellular performance as the battery gets in the way of the radios. For the Smart Battery Case, Apple has incorporated a passive antenna which reroutes radio frequencies and minimizes interference. For sound, the case includes a specifically designed acoustic opening to channel audio from the iPhone speaker.
The company also claims its charging mechanism is better than competing cases. Most cases first charge the phone and then charge the battery pack. Apple’s case can crossover to charge the integrated battery mid-way through the phone charge cycle.