Sine wave generator for full wave rectification

??? What you do depends on how you intend the oscilloscope to interface with an Arduino or other interface or use the audio output of your Android device.

Here are some ideas to consider:

Provide audio output from your Android or a signal from your Arduino (or other interface) to your oscilloscope. You may have to provide an audio amplifier to the speaker audio or output from the minicomputer.

Regards,
Steve