Your magical mirrors could replace 28,000 kilometres (17,400 miles) of Optical Fibres. The total costs of the cables currently laid is estimated to be about 1.1 billion (Source below article).
https://en.wikipedia.org/wiki/Fiber-Optic_Link_Around_the_Globe
In simple terms, the communications happen by having an array of high-speed LED placed across the surface of the mirror, pulsing 1's and 0's in various frequencies of the EM spectrum (infrared, microwave, visible light, ultra-violet). The bandwidth capabilities of such a set-up would be orders of magnitude higher than traditional Optical Fibres. We are speaking of several Peta-bytes per second, using a single pair of 50-inch mirrors here.
You could take this further and have miniature mirrors embedded inside electronic devices and totally replace Radio-waves with mirrors. GSM, 4G, Wifi, Microwaves would all be brutally killed, given the high bandwidth and power-efficiencies of these mirrors.
Our networking protocols are pretty robust and allow interfacing between existing and new communication technologies, pretty easily. So, the new iPhone (or more probably Samsung) might support Pavel Mirrors as the cutting edge communication system. The monetising potential is several Billions for sure.
Since many readers on this site might not be familiar about how optic fibres work, here is an over-simplified description. Imagine you had one of these mirrors placed right in front of a Television Set and another in front of you. But, you are sitting miles away from the television. If you now point your remote-control at the mirror and press a button, it would still work and the TV would switch channels or increase volume.
Now imagine the TV's remote-control sensor is placed right against the mirror's surface and so is the remote-control also placed against the surface of the other mirror (the positioning matters). This would allow you to place multiple remotes and sensors and also run them with less power. Typical TV remotes use Infrared light. But, there are LEDs and sensors available for other kinds of lights, like Red, Green, Blue, Yellow, UV. This means you could tightly pack these sensors and still prevent them from interfering with each other. A cheap TV remote LED can only pulse a few thousand times per second reliably. But, there are LEDs that can pulse trillions of times per second in multiple light-frequencies simultaneously. These are the once used in Optic-fibres and you could use them here too (if you have Trillions of TVs or to send data across the ocean).