Voice-powered virtual assistants were all the rage in 2011. Two years later, they remain something of a novelty feature with untapped potential. Apple (NASDAQ:AAPL) kicked things off in the mainstream with Siri in the iPhone 4S, but Google (NASDAQ:GOOGL) showed the Mac maker how it's really done with Google Now, which is widely considered a superior service.

All the while, both assistants have remained relegated to mobile platforms, even though it seems inevitable for them to find their ways to the desktop. Apple has only added voice dictation to OS X, with no mention of bringing Siri to the Mac yet. There have been hints that Siri will indeed come to the Mac eventually (such as jobĀ postings). When Apple detailed OS X 10.9 Mavericks earlier this month at WWDC, again it said nothing of Siri on the Mac.

Google might upstage Siri once again. CNET noticed that a recent developer build of Google's popular Chrome browser contained hints that Google Now may get integrated in the immediate future. It seems more imminent now because while there were similar hints in December, now Chrome appears to hook up to Google's servers for Now-related notifications.

If Google Now is about to be built into Chrome, which StatCounter estimates has a 41% browser market share, it could easily become the dominant virtual assistant. Google Now is already available on both Android and iOS -- another example of Google services infiltrating the rival mobile platform.

Services are an increasingly important battleground between Apple and Google, and there's no doubt that the search giant currently has the lead. Apple is hoping to beef up its service offerings, such as the introduction of a new Maps desktop app to compete with web-based Google Maps.

Bringing Google Now to the Mac via Chrome could crush Siri's prospects on its home turf.

Fool contributor Evan Niu, CFA, owns shares of Apple. The Motley Fool recommends Apple and Google. The Motley Fool owns shares of Apple and Google. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.