Kevin Werbach on Wifi PBXs

Kevin Werbach notes yesterday on a killer app for Wifi inside businesses: Wifi-enabled PBXs. 

In other words, route their voice traffic within the company over the private WiFi network.  This would save mucho costs, and give the companies features and management capabilities they don't have today.
I wrote about this over a month ago, when TI rolled out a new lower power Wifi chipset.  An excerpt:
Most interesting about this product release is it signals the coming convergence of corporate PBX systems with cell phones.  Equip a corporate PBX system with VoIP over WiFi, and allow it to seamlessly roam to cellular networks when it is out of range of the corporate network, and you've got (a) a single device you can carry around with you that has one phone number, and (b) no cellular charges when you're within range of the corporate LAN.
Kevin, you're dead on - this will significantly enhance the capability and manageability of voice service, and it will also provide a very profitable business model for one or more carriers. Carriers now have a roadmap to a cost-effective service that incorporates the corporate PBX inside the office with cellular service when outside the office, all with the same phone number.