This app was created for testing loudspeakers, but feel free to use it however you like.
There are now three waveforms to select from, the most common is sine wave method of tone generation, it is selected by default as it's the best method to test speakers.
You can use this app to test your car speakers, generate low frequency (usually 45-60 Hz) sound to test your sub-woofers and so on.

DISCLAIMER: I will not be held responsible for any damages arising from use of this application.

Check with your device/speaker manual for allowed frequencies first!!!

Please be careful when using it, don't start on maximum volume, also I would not recommend using it with headphones, especially if you are not sure what you're doing.