While RIM has had MVS for quite awhile now since they purchased the company that created it. Now that they are finally making MVS useful by adding Wi-Fi campus calling using VoIP over SIP connections in v5.0 I think they might have a good solution to sell. The team behind MVS at RIM just released a nice demo video of MVS 5.0 that is coming out later this year so you can get a taste of how it works.
Hopefully RIM will extend this functionality to personal BlackBerry phones by offering a SIP client in the future or providing guidance to developers on how to create VoIP clients for BlackBerry. It really annoys me when even SKYPE decides to make their BlackBerry app work over regular cellphone phone calls instead of data.