Need to get around Dhaka, Bangladesh by transit? It's possible, but you have to know what the buses do. As in many developing-world cities, transit information is almost nonexistent -- to the point that when a startup decided to draw a transit map of Dhaka, the only way to figure out what each bus route did was to ride or follow it!
More on their project here. Making developing-world transit more legible is a really obvious category of "low hanging fruit".