Photo: adman_as (flickr)

How can you help the world's neediest people when you don't even know they exist?

Take Rio de Janiero's sprawling slum settlements, known as favelas. They contain maybe one-third of the city's population, but no one really knows for certain, and the official counts are probably too low. When you consider similar situations worldwide, there are perhaps more than a billion people whose governments have no official record of their existence, says Melanie Edwards.

Her company, Mobile Metrix, hires and trains local teenagers — in Brazil and other developing countries — equips them with handheld computers and sends them door-to-door to get lifestyle information on their neighbors via a 100-question survey.

The idea is that aid organizations, governments and corporations essentially make decisions on where to spend money based on unreliable numbers. Enter Mobile Metrix, which says it "connects the uncounted poor with companies and nonprofits that can meet their needs."

Part of the reason the model is viable is because Mobile Metrix is able to persuade corporations to support its work. When a dengue epidemic infected nearly 250,000 in Rio de Janeiro earlier this year, for example, Mobile Metrix teamed up with Johnson & Johnson to provide favela residents with anti-mosquito repellent and doorstep tips on malaria prevention.

Edwards says each young Mobile Metrix "agent" is paid better than a drug pusher on the streets of Rio and can gain professional skills and a sense of dignity.

"These are capable, untapped human resources. By believing in them, we dignify them and they dignify themselves," Edwards told Rob Katz of NextBillion.net. "We see our employees step into their power — to transform themselves and their community."