Thanks for the response! I'll read up on those acronyms and come back when I understand more.
The 'why bother' is that I'm in the field of ICT4D (Information and Communication Technology for Development), which can be explained as making technology more useful to poor people. I live in South Africa, where millions of poor people own cellphones (at least 13m), but they often cannot afford to use them for normal network use. These cellphones don't have wifi, but many do have Bluetooth.
What I'm looking at is a way to increase the usefulness of technology that is already in the hands of ordinary people, without making it cost more.
Where this gets exciting is the Village Telco concept (see villagetelco.org). If you look at the site you'll see they have developed something called the Mesh Potato, which is a low cost self-contained mesh node that is capable of carrying voice and data. If that can be adapted to include a Bluetooth radio, then you just have to get people into Bluetooth range of the Potato device, and they'll be able to make calls using their own handsets to anywhere else on the network.
It's the killer app for existing technology, if it can be done... which it seems it probably can't

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Regards,
Fritz