Search giant Google ramped up the pressure on Skype, Microsoft and others last week by acquiring web telephony startup GrandCentral Communications for an undisclosed sum.

GrandCentral’s technology allows users to manage all their numbers through one interface and one number that can be applied to ring all, or any of, the user’s phones.

Google product manager Wesley Chan wrote on his company blog that “GrandCentral is an innovative service that lets users integrate all of their existing phone numbers and voice mailboxes into one account, which can be accessed from the web.”

Google is likely to integrate the GrandCentral capabilities with Google Talk and make it accessible through GMail/Google Mail accounts.

Butler Group analyst Mark Blowers said, “Google has realised that to be a credible offering in the future, you have to have a voice element as well. Users will not just want email and instant messaging functions; they’ll want full unified communications features.”

That approach could see Google going up against Microsoft, which in March agreed to acquire Tellme Networks, and Skype.

Blowers said Google is seeking to expand out of its core offerings. “Eventually, expectations are that Google will move to integrate video, since its competitors are moving to offer those features already. I’d expect its next move would be in the area of video comms,” he added.

Google said it will support existing GrandCentral customers but did not reveal its plans for the technology.