T-Mobile is rolling out an update to its Android customers that enables one important new feature: carrier billing. With this feature now working, customers will be able to have Android Market purchases added to their monthly bill rather than their credit card.Carrier billing is a very important step for T-Mobile (and other network operators) to take in order to boost the adoption of the Android platform. Before this week, T-Mobile customers (and pretty much all Android users) needed to pull out their credit cards and make a payment via Google Check-Out if they wanted to purchase software that required payment. That's a huge barrier to a lot of people who don't feel that mobile networks are secure for such things (they are, by the way).

In fact, recent reports have shown that Android owners are far less likely to buy applications than iPhone owners are? Why? Apple makes it easy to pay with an Apple account. Paying a single Android Developer for an application has made it more difficult for Android developers to see the same level of success that their iPhone-developing peers are seeing over in the iPhone Apps Store.

According to T-Mobile, the Market application update will be invisible to end users. No steps are necessary to receive the update, it happens automatically. T-Mobile says that it will stagger the roll-out, and that all users should have the market update no later than December 30.

T-Mobile notes, "Once you receive the update you will be able to purchase paid applications using your credit card or your T-Mobile account. Any applications uninstalled within 24 hours will NOT be charged to your T-Mobile account or credit card." I like the 24-hour "try-before-you-buy" option. That lets people take the application for a spin before committing to it.

Perhaps other operators -- including Sprint and Verizon Wireless in the U.S. -- will enable carrier billing too, giving Android developers a better chance to make a buck.