Source: Apple.

Launched in 2013, Apple's (NASDAQ:AAPL) iPhone 5s had an obvious headline selling feature: Touch ID. Of course, the new fingerprint recognition sensor was built using the technology that Apple received when it acquired AuthenTec in 2012, as if it wasn't obvious enough then what the Mac maker's plans were. Naturally, Touch ID made its way into last year's iPhone 6 and 6 Plus along with the iPad Air 2 and iPad Mini 3.

As is often the case, once Apple pioneers or embraces an innovative new technology, it likes to proliferate that technology throughout its product portfolio. This has been true for things like high-resolution Retina displays, and it seems to be what will happen with Force Touch.

That leads us to an inevitable question: when will the Mac get Touch ID?

It could be different this time around
By no means would Apple be the first computer manufacturer to integrate a fingerprint sensor directly into a computer. Other PC makers tried doing exactly that over a decade ago, but where they fell short was the execution. And it's not as if commoditized PC makers with razor-thin margins and no direct control over the underlying operating system are going to put all that much effort into creating a compelling solution.

Source: Apple.

That's why if Apple implements Touch ID in the Mac, it will be different than previous attempts. Apple is the only company that has all of the pieces of the puzzle (as well as the sway) and can truly put together an end-to-end solution. Touch ID's recognition performance is significantly more advanced than the old-school infrared or swipe-based sensors.

All of the benefits that Apple has already marketed for iOS would be immediately appreciated on the desktop, including things like unlocking your Mac with Touch ID (there are third-party applications that currently offer this functionality) or logging into a website. But those minor conveniences pale in comparison to one way that Touch ID on the Mac could be truly revolutionary: e-commerce.

The real game changer: Apple Pay
As obvious as it was that Apple was going to integrate a fingerprint sensor into the iPhone, it was equally obvious that the biometric security would be perfect for a mobile payments service. Now that Apple Pay has launched and uses Touch ID for authentication, mobile payments are here to stay. But beyond contactless transactions at retail stores, Apple Pay has a whole other side that's waiting to be tapped. The service can be used for in-app purchases made through the App Store, but it's not a stretch of the imagination to apply this same thinking to broader e-commerce taking place on PCs.

Source: Apple.

Imagine going to (which already supports Touch ID for purchasing in its mobile app), picking out an item and instead of having to login or input any other payment information, you just place your finger on a Touch ID sensor built into your Mac. Sure, Amazon already makes it plenty easy to impulse buy, but there are plenty of other e-commerce sites that could benefit from a more seamless consumer experience. Consider the fact that Apple Pay VP Jennifer Baily recently noted that app developers are seeing a 2x conversion rate with in-app purchases made through Apple Pay.

That's an incredible improvement. The conversion rate on a PC likely wouldn't benefit as much since the hurdles to purchasing on a PC aren't nearly as high as they are on mobile devices (who wants to input all that information on such a small screen while they're on the go?), but it would undoubtedly jump.

What's missing?
Naturally, there are design and hardware considerations that Apple is likely thinking about. Designing Touch ID into a Mac will need to keep with the same minimalist aesthetic, but that's all Jony Ive's department. It would be quite simple for Apple to build Touch ID support into OS X. Then it would need to create an open framework that websites could use to tap into the protocol, which is probably the biggest technical challenge. Apps found in the Mac App store could potentially integrate a Touch ID application programming interface (API) relatively easy, but the broader web wouldn't be so easy.

The good news is that Apple isn't the only one trying to kill the password. The Fast IDentity Online (FIDO) Alliance has set out to do just that, and counts most of the major tech players as members.

How would Apple benefit?
If all of this one day becomes a reality, there are several ways that Apple would reap the rewards.

First, it could demand a small cut of the action, much like the 0.15% of transactions that it enjoys with Apple Pay. If Apple Pay on the Mac with Touch ID can really boost purchase conversions, it would be well worth it from the merchants' perspective. Second, there would be a necessary upgrade cycle for Mac users to get their hands on the hardware. This would take quite some time considering the longer (and elongating) PC upgrade cycle. Third, if Apple is the only company offering this type of experience, it can engender even greater customer loyalty through continued differentiation. Fourth, it just sounds like an awesome user experience, which Apple is rather keen on.

It may not be anytime soon, but one of these days I think Apple Pay on the Mac with Touch ID will become a reality. It seems like just a matter of time.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.