Think of it as living together before getting married.

A couple of financial institutions have recently created mobile apps available to anyone as a way of engaging with people through their phones. The institutions are hoping that the apps will build trust with their users and those users will eventually become customers.

Assuming they have credit scores, any consumer can get their three-digit numbers using the CreditWise app from Capital One, for instance. More recently, Ally Bank has been testing a financial health app that anyone could sign up to try. The app, called Splurge Alert, is in limited release.

The general apps follow a slew of fintech apps that have entered the market to crunch financial data and woo consumers on experience. Banks are taking notes — this sort of move is all about the experience. Banks are testing how to develop relationships through financial guidance via mobile apps rather than focusing on products.

"This helps establish their brand with noncustomers, particularly millennials who tend to gravitate to these types of mobile apps," said Alex Johnson, director of credit advisory service for Mercator Advisory Group.

The move also speaks to the evolution of mobile — as banks, mostly the larger banks, have built out their standard mobile apps, they are now exploring what other use cases might make sense to support their customers and potential customers. Other experiments include using the mobile device to connect with other channels and exploring things like Facebook Messenger chatbots to connect with customers.

"It's an interesting inflection point," Johnson said.

Of course, some would argue that the last thing anyone needs is another app. Instead, mobile technology is moving toward a future where there are fewer apps and instead companies use Facebook and others to connect with their customers, some technologists argue. Johnson said that shouldn't dissuade banks from considering general apps.

"Banks shouldn't stop trying to develop front-end applications for targeted use cases (like managing your credit score), which consumers can engage with directly," Johnson said in an email. "We still don't know where most consumers are going to draw the line between financial apps and apps that contain financial insights. It's possible that some things don't belong in Facebook Messenger."

Additionally, Johnson said that apps that provide value outside of the core banking functionalities will help banks try to tackle one of the thorniest problems: how to create sales opportunities at a time when branch transactions continue to decline.

"It's an opportunity to work with noncustomers," Johnson said.

And increasingly, consumers have ever more options to use nonbank mobile apps, like Mint, Qapital and Penny to get such advice. To compete for eyeballs—and to open up the opportunity to sell them something later on—banks are creating something that could be used by one and all.

The general apps are also similar to functions like those that help customers shop, said Nicole Sturgill, principal executive adviser with CEB, in that they go beyond transactions.

Similarly, a handful of banks make portions of their app features available to noncustomers. USAA, a digital innovator, lets consumers view areas of loan calculators, news center, virtual assistant and help to varying degrees before needing to login, for instance. Wells Fargo and JPMorgan Chase are among the banks that have recently updated their unauthenticated mobile banking apps' designs.

Since banks spend so much money on mass marketing, a mobile app has potential to drive more engagement.

"Maybe if you can create a more frequent, deeper engagement with noncustomer then it might be a more cost effective way of marketing," said Oliwia Berdak, senior analyst at Forrester.

However, before exploring general apps, banks would have to figure out how to justify the costs of supporting such apps.

"The really huge question is, 'What's the compelling reason to download this app?' " said Stessa Cohen, a research director at Gartner.

In other words, banks would need to develop a marketing plan around how consumers will find their apps and also provide them a compelling reason to download it.

And whether or not general apps would lead to new customers is debatable.

"We have to wait and see," said CEB's Sturgill. "There is no better proof than the proof."

As with anything, the execution matters most — including whether banks use the apps to spam consumers on offers.

"There are missteps that could make this challenging," Sturgill said.

But as she sees it, the opportunity to add revenue while adding value to consumers is great. After all, consumers are seeking financial guidance from somewhere, if the number of fintech startups focused on that space is any indication.

"They will not care if [guidance] is coming from a bank or startup. It doesn't matter," Sturgill said. "If the app is useful, you will use it."