Screen Off is a free Android application designed to help you lock your phone or tablet quickly without using the power button. This app comes in handy for people with motor disabilities or a damaged power button. You can unlock your device using the fingerprint reader or long-press for the power menu. Screen Off also features a quick settings tile and a resizable widget. The app does not contain ads, trackers, or hidden purchases, and it requires no shady permissions.

Screen Off uses the Accessibility API Policy to lock your device, and on older Android versions, it uses the Device Administrator permission. To remove it on older Android versions, go to "Settings" -> "(Location &) Security" -> "Device administrators" -> Uncheck "Screen Off". It is worth noting that if you still use a task killer/manager, you need to whitelist this application or stop using your task killer. Android has excellent memory management these days.

If you are looking for a simple and useful app to lock your device quickly, Screen Off is an excellent option.