Tech communities are booming all over Africa, says Nairobi-based Juliana Rotich, cofounder of the open-source software Ushahidi. But it remains challenging to get and stay connected in a region with frequent blackouts and spotty Internet hookups. So Rotich and friends developed BRCK, offering resilient connectivity for the developing world. Juliana Rotich is the co-founder of Ushahidi, open-source software for collecting and mapping information -- and of iHub, a collective tech space in Nairobi, Kenya. She is a TED Senior Fellow.