SimonXi
Here is a demo of how it works in action~
All in all, the tech behind is simple, normal HID device such as mouse or keyboard either requires a dongle or a cable which are extremely easy to be found, using a Bluetooth device however, hide the physical presence from our bare eyes.
In bluetooth, there are many functions, BLE HID is one of them, what is does is to simulate your microcontroller as a bluetooth keyboard or/and mouse, and because you are program it, so you can name it to a very misleading name such as your friends Phone name or his/her home audio system name, so that even when he get suspicious and start looking through the Bluetooth list, he will have a hard time finding any abnormallies.
In this project, our AMB23 can be programmed using Arduino IDE into a Bluetooth keyboard and moue at the same time, once paired and connected, it will start sending any the "payload" that you have prepared, it can be a string of charactors or random clicks and drags or even keep triggering some system hotkeys. Your poor friends have no way but to believe that his/her PC has been attacked by some sort of hackers and panic into shutting down the PC XDDD
Disclaimer: This is just for fun, and not meant to cause any damange or loss, please use the info here at your own risk