The problem here is that the problem is exactly the same as any startup -- ideas don't mean a lot. By that I mean that most any idea I could come up has probably been tried before. The trick will be finding a developer who is deeply immersed in the culture of folks they're tying to help and can speak to them.
Anonymously identifying officials that asked you for a bribe. That'd be a great app.
Finding the nearest potable water.
Job search for unskilled workers.
Craigslist for illiterate people (add in geo-location instead of cities)
