There are 4 billion mobile phones in the world, but only 2 billion bank accounts. That's not just a bit of trivia, but the very raison d'etre for the new mobile payment service called BOKU, launching out of stealth mode today. The service essentially turns your phone into a credit card, allowing you to pay for things "by mobile" with the charges showing up on your cell phone bill at the end of the month.

About BOKU

Having only gotten started at the beginning of this year, the team at BOKU has been working at top speed. The company has already received $13 million in financing from Benchmark Capital with participation from Index Ventures and Khosla Ventures as well. They've also acquired two other mobile payment companies, Paymo and Mobillcash, allowing BOKU to start off with a decently-sized customer base and a wide range of participating carriers.

The Virtual Goods Marketplace

BOKU isn't really going up against online payment services like PayPal which requires you to link a bank account or credit card to your account. Instead, not only are they targeting the portion of the online world who don't have bank accounts (but who do have mobile phones), they're also going after an entirely different type of transaction altogether: virtual goods.

Where PayPal has become a popular method to pay for "things" online, BOKU aims to become the standard for paying for "virtual" things - things which include virtual goods in online worlds like Second Life or World of Warcraft as well as in casual games like those found on Facebook, MySpace, and hi5. The company is also working with other game publishers like Gameforge, Aeria Games, and Puzzle Pirates to name a few.

On Facebook alone, there's a virtual marketplace estimated at $500 million in transactions, BOKU's Ron Hirson, Sr. VP of Product Development, tells us. However, the virtual goods market as a whole is worth $8 billion today and continues to grow.

How BOKU Works

The process of paying for these virtual goods via your mobile couldn't be simpler. You just click on the "Pay by Mobile" button provided on the web site, enter in your phone number, and confirm the payment via a text message sent to your phone. The whole process is extremely quick. It's also in many ways a safer way to pay than using your credit card. With a credit card, your number could be stolen and you wouldn't even know until you receive your next statement at the end of the month. However, your phone can't go missing for very long without you becoming aware.

BOKU launches today to serve 1.6 billion customers in 53 countries.