High Power Flashlight - Shake is a free and easy-to-use app that lets you use your phone's built-in flashlight as a signal or as a source of light. It's designed to work with your phone's screen off, so you can use it in situations where the screen is on but the display is off (for example, when you're using a projector at a party). You can also use it to read in the dark, and you don't have to worry about running out of battery.

If you're in a situation where you need to alert people to help you, this app is perfect for you. It has an SOS mode, so you can use it to call for help in an emergency.