Buying a ready-made unit is unlikely. Constructing one would be involved, but has potential. The big problem in third world countries isn't growing the
food, it is getting it to the people before it rots. There certainly are solutions to real world problems, but difficult to implement when you're swimming against powerful tides that benefit from keeping locals divided, destitute and desperate.
I'm a big fan of open source technology and will be looking a lot closer into this kind of thing. Another area is
water; specifically, dew and
fog harvesting, for the folks that can't afford to buy or run a
reverse osmosis watermaker. That's for another thread, though...