The DPH-540 uses Session Initiation Protocol (SIP), and is ready to use with an Internet (VoIP) phone service plan. With echo cancellation, packet delay compensation and lost packet recovery, a VoIP call over a wireless network will sound similar to regular phone service.
Well isn't that just neat! VoIP on a celluar is without a doubt a pretty limited service at this time, with a cell tower being much more omnipresent than a hotspot, but that is changing as time goes with even restauraunts offering wireless connections. Neat stuff, and I'd definitely like to see it in action.