boku 2Mobile payments provider Boku has gained a lot of momentum as a provider of alternate payment for social games.

The company said in September that it’s service was seeing big growth, but it has made more progress now. It’s announcing today that 12 more game developers have signed up to use its mobile payments system. These new companies alone will help Boku reach 200 million more customers who play 250 social and casual games.

boku 1With Boku, game players can use their mobile phone numbers to pay for virtual goods in social games on Facebook and other platforms. They simply enter their phone number when prompted to pay for something. Then they reply “y” to a text message that verifies the transaction.

The San Francisco-based company is also announcing a new user interface, allowing partners to increase their revenue dramatically. It will be interesting to see how much Boku can grow in the U.S.

European and Japanese users have embraced using their cell phones to pay for items. But the U.S. has lagged.

The new game developer partners include 6Waves, Cie Studios, Cyberstep, GameDuell, IGG, King.com, NHN USA ijji, Ntreev, Outspark, PerfectWorld, Snap Interactive and Zoosk. With these new partners, Boku has a number of the top Facebook apps covered. It also has a strong presence on web sites using virtual goods models. Full told, Boku has more than 1,000 merchant partners who accept its payment system in 56 countries.

Boku, a startup competition finalist at our recent MobileBeat conference, is funded by Benchmark Capital, Index Ventures and Khosla Ventures. The company was founded in 2008 and raised $13 million in June. It used a bunch of the money to buy payment firms Mobillcash and Paymo. Rivals include Zong, Obopay, and PayPal.