Banks' race to meet the customers "where they are" has taken on a new twist: customers are now product developers -- not just end users. Last week, U.K. challenger bank Monzo rolled out "Monzo Labs" -- a feature within the app that lets users test new features as they're being developed. It's part of a trend to release product iterations to an ever-larger number of users -- a necessary move to keep pace with changing expectations as the businesses scale quickly. Any Monzo user can test products and offer feedback. The goal of Monzo Labs is to keep customers involved in product thinking as user numbers grow, with the goal to get every Monzo customer involved in some way, said Tristan Thomas, Monzo's head of marketing and community. Three-year-old Monzo, which has 650,000 customers, has been active on various fronts in seeking feedback from customers on products while they're in development -- both through in-person "Testing Tuesdays" at Monzo offices and an exchange of views and polls on its online forums. For instance, Monzo polled users on its forums on how much it should charge for overseas ATM fees, and introduced goals-based savings envelopes called "pots" based on user input. To keep pace with the demands of a growing customer base, the company decided to open up product testing to all interested customers. Monzo labs' inaugural product test is of a feature called "Summary," which does an analysis of a customer's salary and spending habits to predict spending outflows and disposable income. In three days, the Monzo Labs online community forum on its site has drawn in thousands of users, Thomas said. Digital-only challenger banks like Monzo are emphasizing customer involvement to build a human connection with customers -- a move others like Tandem, Revolut and Chime are also emulating. Chime, for instance, recently launched a chat feature within its mobile app that lets customers provide real-time feedback, a tool that's used by around 50,000 users every month, according head of product Zachary Smith. Letting customers take an active role in shaping products instead of passively contributing to user surveys builds a customer community that's invested in the company's offerings and more likely to recommend them to friends and family. "If you think about the three pillars of customer engagement, the first is adoption, the second is [frequent] usage and the third is the loyalty umbrella," Aite senior analyst David Albertazzi. "I see this concept of the Monzo community forum where you're basically turning customers into advocates, and I view that as the top of the pyramid, and those are your engaged customers." all about emotion, cognition and human behavior" -- understanding the customer's mind map as they navigate through a feature, she said. The company emphasized active customer involvement over the past 18 months, and it's currently in the process of releasing a messaging experience for digital account openings. The notion of building out product features with customers instead of only releasing near-complete products is part of organizations' transitions from waterfall to agile product development, acquiring feedback from customers on end-to-end product journeys, Albertazzi said. The challenge of releasing features early is reinforcing to customers that they'll always have a chance to offer input to improve experiences -- long after the feature has gone from beta to mainstream. "We have to find that balance between speed as a startup, getting new features in customers' hands and making sure they work -- it's always a difficult call to make," said Thomas.