There may be five billion people with mobile phones in the world, but most of them don't have a credit card. Systems and software than can help users turn cash into digital goods are sorely needed. That means things like carrier billing, which turns out to be a great way for developers to make some revenue. Fortumo is at the Samsung Developers Conference and we had a chance to talk to them about it all.

We tend to always think of the way things work in the west, but as Tarvo explains, in areas like South East Asia or Russia, carrier billing is actually the preferred method of paying for our digital purchases.

Fortumo can help developers make money all over the world. If you're a developer, drop by their website and give them a look.

More: Samsung Developers Conference portal