The credit union's ArrowGeeks, largely recruited from California State University San Bernardino, University of California Riverside, and University of Redlands, held in-branch sessions for online banking and the mobile app, which drew as many as 60 members at a time.

"Our ArrowGeeks are amazing—not only do they know online banking inside and out, but they are so patient and friendly," Friesen said.

Within 24 hours of launching its app in early July, Arrowhead CU had 5,600 downloads. One week later, it was up to 16,000 downloads and today, it has more than 20,000 downloads, according to Arrowhead CU.

The high number of downloads in just a few weeks was not a surprise to Arrowhead CU, Friesen said, because nearly 70% of its members read their emails on a mobile device, while only 32% read their emails with a desktop or laptop computer.

"We want to provide options to our members, so they can interact with us in the way that suits their lifestyle," the marketing vice president said. "Our members still love our branches, but they also want to be able to check their balance, transfer funds, or pay a bill from their phone while their waiting in a drive-thru."

For its mobile app, Arrowhead plans to add mobile deposit and introduce a personal finance management tool to its online banking site.

Although Arrowhead CU previously had a form of mobile banking, this is the credit union's first app provided by Wescom Resources Group.