Smartwatches may not have ascended to "essential tech" status just yet—their primary features are already capably handled by our smartphones—but they excel as convenience products because they literally put the features we want close at hand (no pun intended).
There's also a side benefit to smartwatches: They're a boon to politeness. After all, glancing at a watch is less intrusive than excavating a phone and checking messages while someone's trying to talk with you.