Fitbit, the biggest company in fitness tracking, has announced that it's acquiring Coin, the maker of a "smart" credit card that digitally holds all of your other credit cards on a single device. But Fitbit isn't buying Coin for its current Coin 2.0 gadget; that's actually being left out of the deal and Coin says its existing products can be used until their internal batteries die. Instead, Fitbit's primary interest in Coin is the company's work on wearable forms of payment.

It's not difficult to imagine using a future Fitbit tracker as a mobile wallet for on-the-go purchases; smartwatches already do it, after all. And the Up4, a product from Fitbit's big fitness rival Jawbone, can make mobile payments with American Express cards. In January, Coin announced that it would be working with MasterCard to help other companies build mobile payment NFC chips into a wider variety of devices.

Fitbit is being up front about the fact that it's too late to integrate Coin's technology into any other products coming out this year. In a press release, the company acknowledged "there are no plans to integrate Coin’s wearable payments technology into the 2016 Fitbit product roadmap." But that certainly leaves the door open for something next year, as the Coin purchase "accelerates Fitbit’s ability to develop an active NFC payment solution" that could eventually find its way into Fitbit's fitness tracker family.

The acquisition is already a done deal; Fitbit says it closed last week on May 12th. Coin Rewards and the Coin Developer Program are being shut down immediately, but existing Coin cards will remain under their one-year manufacturer's warranty and continue functioning until the battery gives out. No additional units will be produced.

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