When McDonald's (NYSE:MCD) reported fourth-quarter earnings last month, it became clear that the fast-food chain isn't out of the woods just yet, as it reported a drop in comparable-restaurant sales for the first time in six quarters.

Things are likely to get even more challenging because McDonald's restaurants will now be competing against last year's improved results, fueled by the addition of all-day breakfast.

But don't count McDonald's out just yet, as the hamburger chain is rolling out what may be its biggest innovation yet: The Big Mac ATM.

"Be still my beating heart, for an instantaneous Big Mac machine is now a thing," one blogger wrote.

And the machines aren't just a theoretical concept. One is already up and running at a McDonald's location in Boston, where the wait to try it out has stretched to an hour or longer at various times.

A McDonald's Big Mac.

Will Big Mac ATM's soon be at a location near you? Image source: McDonald's.

To be clear, just like an actual ATM doesn't make money, a Big Mac ATM doesn't make Big Macs. It merely dispenses pre-prepared Big Macs.

"The burgers are cooked on-site at McDonald's and then immediately loaded into the heated machine, which is refilled on an ongoing basis to ensure fresh quality," explained the owner-operator of the location where the unit was installed.

At this point, the technology is still in the testing phase. McDonald's has said that it has no plans to roll out more of them in the near future.

Yet, it doesn't take an enormous stretch of the imagination to see how this could evolve the way McDonald's serves its customers. The chain has already installed self-order kiosks at locations around the world -- I used one in Spain last year and loved it.

Given that the Big Mac ATM is necessarily coupled with a self-ordering kiosk, the technology not only eliminates the need for a cashier, it also does away with the person who assembles the food on a tray or in a bag.

As the technology develops further, it isn't hard to see how these could reduce the size of restaurants and even speed up the ordering process.

I'm a closet McDonald's fan and must admit that my heart tingled a bit at the mere thought of a Big Mac ATM.

And as an investor, I can't help but think that further automating the process will eventually lead to more consistently prepared food, as well as a shorter wait time, the nexus of which is what McDonald's is all about.

John Maxfield has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.