Citigroup's year-old fintech unit is suddenly making its presence felt — and perhaps giving a taste of the direction other banks might go in trying to put more financial services directly in their customers' hands.

Citi FinTech said Monday that it has built a mobile-first experience for Citigold credit card members that offers access to retail banking and investment accounts and includes a click-to-call button so they can immediately reach their relationship managers, financial advisers or a 24-hour service center.

Specifically, Citi is bringing wealth management services into the online banking platform. Its high-end credit card customers are now able to buy and sell equities, exchange-traded funds and mutual funds as well as initiate real-time trades within the same mobile experience. In the coming days, they will also be able to open brokerage accounts in the app.

The fintech unit took inspiration from the best fintech apps, collaborating with startups as well as about 2,500 Citigold customers to ensure the bank was responding to their needs, said Carey Kolaja, global chief product officer for Citi FinTech. Citi built features in a series of two-week sprints in recent months, allowing it to quickly modify the product and adjust it for different client needs and markets.

"Our goal was to start decomposing what's out there today, so as we look at different customer segments, [we ask:] How do we start to curate the experience for you?" Kolaja said. "The intent isn't to force everything into this app, but rather to curate it so it fits customers' needs."

That blend of convenience and customer control is what more banks should be going for in their mobile offerings, said Dan Latimore, senior vice president in the banking division of the research and consulting firm Celent.

"That hands-on, involved consumer is only 10-12% of the population," he said. "As much as [we] talk about mobile banking, overall penetration of folks who have even downloaded the app, much less actually use it on a consistent basis, is still only at 50% or 52%. There's a huge spectrum of folks who aren't digitally mobile — or mobile-ly digital — yet. Bankers want to get them digital to help improve relationship but also lower cost to serve."

One reason Citigold members emerged as the right test bed for the bank's new mobile approach is that they have qualifying balances of $200,000 or more. They each have a dedicated relationship manager and financial planning adviser and receive access to market research.

"We have a lot of clients with a tremendous amount of wealth under management here at Citi," Kolaja said, noting that many of them have E-Trade or other accounts.

"You look at assets under management and where customers are putting their funds to do some on-the-side trading, and the reality is we have that to offer, too," she said. "How do we look at that spectrum of what they want to do and make it easier for them?"

Citi did not indicate any immediate plans for a similar offering to a wider swath of customers, but Kolaja did not rule it out. However, for now, Citigold customers who are iPhone users are the test audience for the mobile-first experience.

The scaled rollout follows additional mobile app enhancements, including dispute resolution and in-app replacement-card tracking. Moreover, credit card customers may lock accounts if cards are misplaced or stolen, view and download statements, receive free FICO scores and activate debit cards through the mobile browser.

Citi is employing facial, voice, PIN and fingerprint biometrics to authenticate at login, although customers can still opt to use a traditional password. It is also putting domestic and international transfers between Citibank accounts in the mobile product and allowing clients to make transfers between linked checking and brokerage accounts using just account numbers.

"A large percentage of our customers, about 70%, use other brands to move their money because it's easy, fun, easier to do; it's instant settlement, it's transparent, it's low cost to zero cost," Kolaja said. "At Citi the need is still the same, but we haven't shown up in the experience way in solving those barriers to usage."

In November Citi made some of its application program interfaces available for third-party developers to foster collaboration and partnerships between fintech companies and consumer brands. Mastercard, Virgin Money and others are already leveraging Citi APIs to create customer solutions. The partnerships it forms through the developer hub are part of what it intends to do "for years to come," Kolaja said.

"You've seen a lot of companies become more of a platform play," she said. "Our intent when we went after this was not just to compare ourselves with other financial institutions but become a global developer platform in the realm of Stripe or Google or others. How we communicate with a new customer base, we believe, is paramount for success."

The convergence of basic banking and wealth management will permeate throughout the banking industry, Kolaja predicts. All different financial services will become even more connected, she said. The most important components are, and always will be, trust, choice and contextualization, she said.

"In the last three to five years we've seen a lot of single-use-case apps. Digit's a great example," she said. "If an algorithm like Digit is able to identify that you've got additional money or you've spent less than you have, [and] if you can dispute a charge to get money back or price-rewind to get money back — the ability for a consumer to make a decision about what to do with that money goes beyond wanting to save it to wanting to invest it [or] maybe pay off a debt or save for a college fund or treat yourself."

Corrected December 5, 2016 at 1:38PM: An earlier version of the graphic that accompanies this story mistakenly said that Gavin Michael replaced Heather Cox as consumer tech chief. Cox was the head of Citi FinTech; Yolande Piazza is her interim successor. An earlier correction misidentified Piazza's direct supervisor. She reports to Stephen Bird, CEO of global consumer banking, not to Michael.