The story behind that phone is cool, but I think the important part is the guy's analysis. This phone is becoming popular because it solves a couple of practical issues specific to parts of the African market at the moment. However should someone design a smartphone specifically for that market, focusing on battery life, I'm sure that these power bank phones would disappear.
Thus we probably shouldn't spend energy making something specifically for a phone like that, whose popularity might drop as fast as it rose when a better solution to those problems appears. If we happen to have something that works on that phone and get it on there, great. But spending too much energy on its might be a little futile, as it might not stick around for very long.
IMHO if we make a light app that can work with patchy network, consumes very little power and works on underpowered phones, basically the least common denominator, it might find its uses in those places. What I'm quite unsure, however, is whether the UX and the content we'd deliver would be interesting to people in that market. We shouldn't let the engineering cool factor of making a light app be the starting point (it's very tempting!), the users should be.