Blending mobile VoIP and call-through

I see that Truphone has launched a call-through add-on to its service. This is a bit like iSkoot with Skype, or various other pseudo-mobile-VoIP services like Jajah and Mobivox. This makes a lot of sense. I expect quite a few of the players in the space to attempt to bundle together: VoWLAN from home or hotspotVoIPo3G when 3G coverage & flatrate data is availableCall-through which exploit users' bundled GSM minutesA PC client as well as handset-based callingThere's no point in having a "on