Massive phased array that could potentially support multiple spot coverage. You still need a bunch of satellites to ensure continuous coverage unlike GEO birds that can cover a whole continent so it will be awhile until you can get worldwide (or nearly worldwide) coverage. With a really fancy DSP box and enough bandwidth, you can account for Doppler. The speeds won't be great but it will certainly be good enough for voice and SMS.

Adding things like mesh networks, you could drop a small server rack and generator at any where in the world and create a robust cell network to cover disaster zones.