Sony may have added mobile payment functionality to the European PlayStation Store, US gamers haven't been able to enjoy the same conveniences -- until now, that is. As of yesterday, all PSN users will be able to log into their Account Management page and choose the "Use Mobile" option.
After entering your mobile phone number you'll be able to add funds via SMS, which will appear on your next phone bill. While I don't see a whole lot of people using this, options are a great thing, and I can see myself doing it every so often when I'm away and about to miss a big sale.
Mobile Billing [PlayStation Blog]