With each passing day, speculation mounts regarding what amazing functionality Apple (NASDAQ:AAPL) might introduce in its upcoming iWatch device. So far we've seen claims of everything from wireless inductive charging, to a curved OLED display, to at least 10 sensors to track health and fitness. And there's little doubt Apple's iWatch already exists, especially given the supply chain reports that surfaced two weeks ago saying it's set to enter mass production sometime this month.

But for all the exciting new applications an iWatch could enable, there's another surprising feature that not only already exists, but also could prove the iWatch's key differentiating factor: voice messaging.

"Actually LOL. OL."
Apple introduced voice messaging in its recent previews of iOS 8, quipping that you'll soon be able to "Actually LOL. OL."

But in all seriousness, Apple also insists that recording voice messages will be as simple as touching and holding a new microphone button with your thumb, then swiping upward to send. At this point, however, the only visible applications Apple has showcased for voice messaging are depicted on its latest iPhones:

Apple stock, iWatch

Apple recently unveiled voice messaging for iOS 8, Credit: Apple.

Now don't get me wrong; Voice messaging seems like a solid value-add for Apple's iPhone users. But it still requires they pull the phone out of their pocket and speak into it. What better way for Apple to provide incremental convenience to consumers than by perfecting voice messaging on a more accessible wrist-worn device like the iWatch?

UBC analyst Steve Milunovich weighed in on the topic earlier this week after meeting with Apple CEO Tim Cook, and notably stated that Apple's voice messaging "could aid penetration of China, which Cook said has a ways to go." Specifically, Milunovich said when their conversation turned to the potential for voice messaging, Cook described a trip to China during which he observed many people already walking down the street speaking brief messages into their phones instead of texting.

It's a fairly safe bet that few people will be willing to tap out an entire text message on a tiny smartwatch display. And while voice-to-text is a viable alternative, it's an imperfect -- albeit improving -- solution prone to occasional inaccuracies. But if Apple can truly port an elegant solution to pioneer voice messages outside with its iWatch, it could be just the push consumers need to make the device a smashing success.