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