As mobile banking gains traction, here's what consumers should know. Thinkstock By Lisa Gerstner, Contributing Editor From Kiplinger's Personal Finance, March 2015 Banking by smartphone is starting to catch on. More than one-third of all U.S. customers’ interactions with their bank in 2014 were via mobile devices, according to a study from consultant Bain & Co. That’s even more than the number of online interactions. Among the most popular features are the ability to monitor account balances and transactions, transfer money between accounts, and pay bills. Many banks also allow you to set up alerts when your account balance is low or there’s a large withdrawal.See Also: Why You Should Try Your Bank's Mobile App Depositing checks via banking apps is gaining traction, too. In most cases, it’s easy and convenient: You follow the instructions to snap photos of the front and back of a check and send the images to your bank. But a Pew Charitable Trusts study found that banks often aren’t transparent about the fine print that governs remote check deposit, including fees, eligibility requirements and how quickly the deposited funds will be available. Some of the large banks surveyed, among them KeyBank, impose a fee of 50 cents per check deposit. Of the banks that made their policies on funds availability clear to prospective customers, most said the money would be available one to two days after posting to the account. The maximum customers could deposit per month varied from as little as $2,500 to as much as $750,000. When in doubt, contact your bank about the conditions of using any mobile services it provides. Look for banks to introduce innovations that may soon become standard. For example, BBVA Compass and U.S. Bank customers can now take a snapshot of a paper bill payment stub and set up recurring payments through the bank’s mobile app.