Remember how I talked about BancorpSouth's expansion into mobile banking last week? Soon enough, they and the three other banks working with Cingular/AT&T Mobile to bring mobile phone banking to customers won't be alone: Citibank announced on Monday they're launching a service of their own, seeing mobile banking as another way to expand service to customers who can access their money online, at ATMs or at branch locations. Unlike the AT&T solution, the Citibank service uses a piece of software the user need to download to their phone. This delivery method, while free to use, may incur a data charge from the wireless provider, but has the advantage of working with all of the major US wireless providers, instead of tying users to AT&T. Citibank is testing the new software in Southern California first and expects to have it working across the US by the middle of the year.