EtchDroid is an open-source application that helps you write images to USB drives.
You can use it to make a bootable GNU/Linux USB drive when your laptop is dead and you're in the middle of nowhere.
Supports raw disk images and most GNU/Linux distributions ISOs
Supports Raspberry Pi images (extract the ZIP file first; use a SD to USB adapter, the internal SD slot is not supported)
Supports most DMG disk images (beta)
No root - everything is done within the bounds of the Android API
Free as in freedom
Write common GNU/Linux distro in streaming from the Internet without storing it on the device
Support for Windows installation ISO (will likely require root)
Support for Unetbootin-style image flashing
Source code is on GitHub: https://github.com/Depau/EtchDroid