Fortumo is a specialist in mobile carrier billing, which lets users to pay for apps and goods in apps without coughing up credit card numbers. 
Fortumo says it integrates with 300 carriers across more than 80 countries, along with over 81,000 developers. Those include long-standing agreements to provide carrier billing services to Angry Birds maker Rovio, Pop Cap Games and Badoo, and it also powers the in-app payments for Windows 8 apps.