Much like GPS is able to track your precise location outdoors, the 802.11mc Wi-Fi standard will be able to do something similar indoors. This feature is generally referred to as RTT, or "Round Trip Time."
Why Would I Want This?
In a world where everyone is concerned about privacy, the thought of your phone not only tracking your outdoor movements, but also where you go indoors can be a bit rattling. Fortunately, there's some really awesome practical application here.
The biggest reason 802.11mc will be a game changer is for indoor mapping---especially in large facilities. For example, if you go to a mall you've never been to before, instead of staring at the "You are here" board and trying to figure out where you want to go, you can pop out your phone and navigate there. Indoors!
And that's just a simple example. Museums, warehouses, large supply stores, and other similar facilities will be able to take advantage of this. But my personal favorite use for this will be a big one: hospitals. Most hospitals are big, confusing places. Indoor navigation will make it a breeze to get to where you're trying to go, especially when your mind more occupied with why you're at the hospital than finding your way around.
There are also practical home uses, too. For example, if you have multiple smart devices in your house---smart lights, for example---you could ask a digital assistant to "turn on the lights" and it would be able to pinpoint which room you're in and only turn those lights on without the need for you to say "turn on the lights in the master bedroom." I'm sure there will be many more uses once this tech becomes more prolific, too.
Cool, So How Does it Work?
The way 802.11mc tracks your location is pretty simple. Basically, it measures the time it takes for a signal to travel between your device and the access point. When multiple access points are part of the equation, it can use the data from all these together to triangulate your location.
In theory, your phone wouldn't even need to be connected to the Wi-Fi for this to work---it should be able to ping the access points and triangulate a precise location without requiring connection to said access points.
But What About Privacy?
Devices that use 802.11mc should require location tracking to follow the same protocols as outdoor tracking. Apps will need to request location permissions and this data will be anonymous just like with outdoor tracking.
This is already clear in the upcoming version of Android---Android "P"---and other manufacturers will undoubtedly follow suit.
Image Credit: Google/Android Developers Blog