In India, friends intentionally call each other, let it ring once or twice, and hang up. That's their way of sending a signal, like "I'm home safe," without being charged for a call in a country with pricey telecommunications and limited Internet accessibility. California native Valerie Wagoner moved to Bangalore, noticed the missed calls, and is now responsible for 416 million of them: That's how many times people have used her company, ZipDial, to connect with brands including Gillette, Disney, Procter & Gamble, and IndiaInfoLine.

It works like this: She issues the brand a number, which it prints on its ads. Consumers call, hang up, and get a text or call in return--and thus are entered in contests, receive coupons, or place an order. In 2013, she expanded to Sri Lanka and Bangladesh, and is now setting up in Indonesia, Singapore and the Philippines.

"Half the world's population needs a better, more accessible mobile experience," Wagoner says. She was once part of eBay's international marketing team, but wanted to be truly involved in emerging markets--and knew she couldn't do that from the Bay Area. "I was a rare entity, a foreigner and a woman running a startup," she says of her early, rough start. "I didn't know the right jokes in Hindi or come from somebody's hometown, but I knew when to wear a sari."

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