There are several computers in the form of USB sticks available on the market at a variety of prices. One of those that really stands out is that That's it - a tiny ARM processor that fits perfectly inside the USB port on your computer.
Tomu is based on the Happy Gecko EFM32HG309 Arm Cortex-M0 + from Gecko's microcontroller from Silicon Labs operating on 25 MHz. It has 8 kb RAM and 60 kb flash. Despite its small size, it supports two LEDs and two touch keys that control the capacity.
Once you connect this small computer, you can simulate a hard disk or mouse and send MIDI data. Tomu is an open source project that can work as a Universal Second Factor security token. The hardware is fully documented and the bootloader as well as the rest of the code is accessible to GitHub.
You can also convert the USB hub to a power switch for your computer. Tomu is not a complete computer because of its limited entry / exit options, but it's definitely an exciting tool for those who want to deal with open source computers.
Tim Ansell, the designer of Tomu, says the YubiKey 4 Nano is the inspiration behind this tiny computer. Its software still requires improvement, but the necessary bootloader code is complete and working.
You can buy Tomu from Crowd Supply starting at the price of $ 30. Just make sure you do not accidentally lose this extremely small PC while cleaning your office!