Simple (formerly BankSimple) announced Wednesday its long-awaited Photo Check Deposit feature.

The add-on to the branchless bank's mobile app will allow users to deposit checks using a smartphone camera — giving customers a new way to place cash into their Simple accounts.

Roughly three weeks ago, Simple rolled out a preview of the feature with an initial group of nearly 300 customers, said Josh Reich, chief executive of the parent company Simple Finance Technology Corp., in an emailed statement. That group was expanded to roughly 750 the next day and grew to more than 4,000 last week.

"Today's addition of Photo Check Deposit represents months of hard work by the Simple team," he said, in the email. "Our customers are sharing their enthusiasm over Twitter and with our customer relations team. And best of all, today's news is prompting many of our customers to ditch their banks and switch to Simple."

Simple set out in 2010 to build "a bank that doesn't suck," Reich has previously said. Since then it has signed up thousands of initial customers that are beta testing the product.