Research In Motion (RIM) made a number of significant announcements last week, for both its consumer and enterprise customers, at the first annual BlackBerry World Conference, formerly known as the Wireless Enterprise Symposium (WES).

But mostly lost among the news of new BlackBerry smartphones, video chat for the BlackBerry PlayBook tablet and a product that will let BlackBerry administrators manage iPhones, iPads and Android devices via BlackBerry infrastructure, was the announcement of a new version of RIM's BlackBerry Mobile Voice System (MVS), v5.1.

BlackBerry MVS connects with RIM's BlackBerry Enterprise Server (BES) to let corporate users securely employ their BlackBerrys to answer calls placed to their organisations' desk phones and smartphones, as well as make calls via BlackBerry that appear to originate from those desk phones, among other things.

In other words, BlackBerry MVS merges enterprise users' smartphones and desk phones, and lets them access corporate phone system features like hold, transfer, conferencing and extension dialling, all via BlackBerry. And BlackBerry MVS 5.1 adds a few new features that enterprises are sure to appreciate.

Most significantly, BlackBerry MVS 5.1 now supports voice over Wi-Fi calling via both Avaya and Nortel corporate phone systems or PBXs. Jeff McDowell, RIM's senior VP of business and platform marketing, says this is notable because Avaya and Nortel are among the most popular enterprise phone system providers, and MVS features will now be available to a much wider user base thanks to v5.1.

BlackBerry MVS 5.1 also packs cool new Wi-Fi features that notify users' when Wi-Fi signal is weakening, so they're aware if a call is about to be transferred to a cellular network or they're about to lose Wi-Fi coverage, according to RIM's Tom Goguen, RIM VP of collaboration and social networking. And on the flipside, MVS 5.1 notifies BlackBerry users on cellular networks when they're in range of a compatible Wi-Fi network, so they can choose to seamlessly switch to Wi-Fi calling.

Finally, the upcoming version of BlackBerry MVS has been rebuilt for higher compatibility with third party applications and phone systems via new support for SIP and VoIP gateways. A "Universal SIP connector" has been added to MVS to enable other phone system makers to tailor their specific VoIP offerings and applications to MVS, according to RIM.

Vendors Mital and Vocera Communications have already employed this new direct SIP connection to MVS to enable both Mital Mobility for BlackBerry MVS 5 and the Vocera Connect Wi-Fi client for BlackBerry, RIM says.

Check out a video demonstration of MVS for more details. And learn more about BlackBerry MVS on RIM's website.