WiFi Kill is a new application that's currently appearing on a number of Android handsets. It's an application which allows you to remotely control your smartphone via Wi-Fi, or BLE (Broadband Internet) in order to protect it and keep it protected. In short, this is a feature that allows you to use your smartphone to gain access to the internet without any hardware requirement (no Bluetooth device or SIM card required). Here's how this works:
The WiFi Kill app will monitor the amount of available wifikill bandwidth on your device. After choosing a frequency to connect at (which can be manually chosen by going into the device's settings), the software will start communicating with your computer. It will connect to your device via its own dedicated SSID (string) and pass this information along to the computer. From there, the computer will establish a connection to the actual wireless router. This way, no one else can interfere with your connection, and you can freely use all the bandwidth that your device has available. The only requirement is that you have a relatively modern smartphone - which should be a Galaxy S4 or higher.
The best thing about the WiFi Kill android app is that it requires absolutely no configuration on your part. All you need to do is scan a new frequency on your own and then configure the connection accordingly. This means that even if you don't have any wifikill devices available (and you're pretty unlikely to do that), this application will still work for you. It's especially great for those who travel with multiple wifikill enabled devices, as it makes it easy to quickly switch from one to another in case of any conflict.