Imagine you're watching PBS right now and Bill Nye The Science Guy comes on. Suddenly Bill Nye's disembodied head is floating across your screen, with 1s and 0s streaming in and out of his ears.

"Did you know," shouts Bill Nye (I don't know why he's shouting, but he is), "that when you make a cellular phone call your voice is transmitted as digital data, just like how a CD or DVD stores information?"

You change the channel. You knew this already, Bill. Everybody knows this. And yet when you make a phone call from your couch, to tell your friend that Bill Nye is "losing his edge," the digital data of that phone call isn't routed over Wi-Fi through your home's fat internet pipes. Instead your carrier confronts some laws of physics and gets those 1s and 0s from the little brick in your hand to a cellular tower that's miles away, which then sends the call over a mess of wires, pipes, and lines that dates back to Alexander Graham Bell himself. It's all very impressive, but who are they trying to impress? Certainly not your dormant Wi-Fi router, certainly not your bitrate-weathered ears, certainly not Bill Nye.

Unless, of course, you use T-Mobile's Wi-Fi calling service. Fun fact: T-Mobile has a service called "Wi-Fi calling." Have you ever heard of it? T-Mobile hopes you haven't.

Wi-Fi calling was originally launched as "HotSpot @ Home" in 2007 by T-Mobile as a bid to compete with the landline. It was a reasonable idea, after all: by providing a reliable service inside the home, a cellphone could replace the stalwart landline, whose only technological advantage in 2007 was reliability and voice quality. Built on the little-used UMA standard, the service shipped on a couple of specially Wi-Fi-equipped mid-range featurephones and was promptly forgotten.

UMA stands for "Unlicensed Mobile Access," and describes any method of taking a voice or data connection and sending it over an "unlicensed" internet connection (anything that's not the carrier's own network) straight into the carrier's nerve center, where it's switched into the regular phone network. Security is maintained due to the unique SIM in each GSM phone.

After HotSpot @ Home launched in 2007 to little fanfare, as a $10 monthly landline-killer, two things happened to vindicate T-Mobile's strategy:

1. Apple launched the iPhone, which marked the beginning of the "smartphones are for everybody" era. 2. Everybody decided they could replace their landline with a cellphone after all.

Unfortunately, these two trends, while growing in parallel, haven't complemented each other very well in the past five years.