USAA, a bank which caters to the military, said that $1.5 million in checks have already been deposited via an iPhone app, which launched just three days ago. Users, who download the app can make deposits by taking photos of both sides of a check. The slips of paper can then be thrown away.

A spokesperson told us that the app has already been installed nearly 150,000 times, and more than 58,000 users have already elected to update it. The bank is currently working on creating a BlackBerry, Palm (NSDQ: PALM) Pre and Google (NSDQ: GOOG) version. In a press release from Monday, USAA said its customers have conducted more than 13.3 million mobile transactions so far this year, which is twice as many as in 2008, and that its adoption rate for mobile services is 14 percent — or three times greater than other banks. That probably has something to do with the fact that it doesn’t have physical branches and is used primarily by people in the military.