Optiboot (an older version) is installed by default on the Arduino Uno and (as of 2018) official Arduino Nano boards. It can be installed on all older mega8, 168 or 328 based Arduinos. As of 2019, ...

USBKWA (USB Keyboard Web App) turns a large tablet or any device with a Web browser into a USB keyboard. Anyone having difficulties using a regular keyboard may find a touch keyboard easier to use.