Termux

Termux is an Android app that provides a terminal emulator and Debian-like Linux environment. Smartphone screens are relatively small compared to a laptop or full computer monitor but screens continue to improve making terminal use increasingly viable. My Google Pixel XL has a 5.5 inch screen running at 2560x1440, the same resolution as one of my desktop 27 inch monitors.

Vertically the terminal is restricted to 57 columns but is surprisingly usable with the on screen keyboard. Held horizontally and paired with the Logitech K380 Bluetooth keyboard, it is an excellent text terminal. Features abound, from an API exposing hardware remotely via ssh, to style support including Powerline fonts.