Hello! This is interesting project. I'd like to use PIC16F886, PIC18F2550 or similar @ 20MHz (up to 48MHz for PIC18F2550 ). As I understand you need the F14 device which will be controlled by audio signal. The audio command is modulated by frequency (2500 Hz - logical 0 and 250 - logical 1, duration 60ms). The packet consist of start sequence, frequency, amplitude, waveform type, active flag and end sequence.
I am planning to use digital potentiometer for the amplitude regulation. Some parts is necessary for DC-DC converter (it can be driven by PIC PWM). We can discuss details later.
I will provide schematic, source code, and results of prototype testing.