Turn an old book into a covert server with a Raspberry Pi Zero and a battery for approximately $80 (USD). In its most basic form, it is just a Raspberry Pi Zero, a 6600 mAh LiIon battery, and a USB LiIon charger. However, it can be extended to include whatever bells and whistles you want, like a display or an external HDD/SSD.

It consists of 3 distinct parts: the backend, frontend, and display. The backend is written in Golang and enables all the online functionality such as messaging, file storage/sharing, and user accounts. The frontend is pure JavaScript with Bootstrap 4 as styling to make it look nice. Finally, the display is an optional OLED 80x128px display that is driven using Python.