But mostly lost among the news of , video chat for the BlackBerry PlayBook tablet and a product that will let BlackBerry 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 organizations' desk-phones and smartphones, as well as make calls via BlackBerry that appear to originate from those desk-phones, among other things. (Read more .)

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 dialing, 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 seamless switch to Wi-Fi calling.