What it appears to be is a portable digital TV without the screen. You don't need a connection to the Internet or through a cell phone because you are capturing the digital signal of a conventional TV broadcast over the air. That is why the advertisements will tell you that coverage is very limited.
I doubt that this will catch on to any great degree for two reasons.
1. Most people watch a lot of cable now and this device will not pick up cable.
2. You can buy a variety of devices that have this technology plus a TV screen so you don't have to buy this and attach it to a monitor.
3. Many of the alternative devices, with a screen, are cheaper than this device.
A variety of them are for sale on Amazon. Search portable digital tvs.