[Kevin Sevcik]

Ryan, again, you can customize the CCP output to produce different frequencies. Not a LOT if you want it to sound half decent, but still probably 3-4 distinct tones. Honestly, with just two tones and a little clever programming you could get several different signals by pulsing and alternating the tones at intervals, sort of like morse code or the BIOS beep codes computers use.

Addressing Alan's comments, yes putting a capacitor in series with your amplifier or speaker would remove the DC component of the signal, but if you're planning on using a bipolar amplifier of some sort to power your speaker, then I'd recommend the extra trouble of a little active filtering, as it would really help in the long run. What I wouldn't recommend is running he speaker directly from the RC digital output. I don't think they can source or sink nearly enough current to work well in that application.