A simple soundboard application. Save some MP3 or OGG files to your phone, load up the app and play them at the touch of a button.
To keep the sound playback levels constant, the app allows you to set a volume level independent of the current volume. On playback, the app sets the volume to that level, plays the sound clip, then returns the volume to it's previous level.
In addition, audio can be created within the app, using text-to-speech, DTMF (phone keypad) tones, and a tone generator.
Designed to be used with phones using an adapter such as the one described at http://www.darkmidnight.co.uk/2016/03/another-telephone-audio-interface.html the app also works well with Xbox Live headsets (Xbox 360), and in theory should work with any device you're capable of connecting your phones audio output to.
See http://www.darkmidnight.co.uk/2015/03/how-to-extract-audio-clips-from-youtube.html for a guide on creating sound clips from YouTube videos and other online sources.