As former Apple employee Bruce Tognazzini recently wrote on his blog AskTog, its main role will be to carry out tasks and other functions "that extend the capabilities of your other devices."
One of the most exciting possibilities is that the iWatch could ensure you never lose your iPhone again.
Granted, Apple already offers Find My iPhone, but that really only comes in handy after you've already lost your phone. And it's a pretty stressful experience when you're looking at iCloud's map, just watching your iPhone move farther and farther away from you.
But with the iWatch, as soon as you start to move out of range from your phone, the iWatch will detect that and immediately alert you.
Crisis averted.