If anyone has time to help, I will summarize my requirement in one line: I require a circuit that can detect the presence of a 2Hz square wave.
I bought a extremely cheap bluetooth module from China that looks like this JY-MCU module: http://www.dealextreme.com/p/jy-mcu-arduino-bluetooth-wireless-serial-port-module-104299
This thing is very nice for the price. I can hook it up very easily and receive serial messages as if a wire was connected. The cons to this product are 1) no documentation at all. There is no datasheet for this device, and any datasheets that you find will probably be wrong. 2) no reverse voltage protection. (I cooked one of these already. this is my second.)
I want to be able to upload sketches with this thing. I have already changed the baud rate to 57600 for my Arduino Nano and am now at the point where I can hit upload and press the reset button at a certain time and it will upload, but I want auto-reset. There is an LED on the bluetooth board that blinks when disconnected and is solid on when connected. For many hours, I have looked all over the board for a simpler indicator and cannot find anything, so now I need to make a circuit that pulses a reset pin whenever the ~2Hz square wave turns solid 3.3V.
I had a friend with a larger bluetooth module with a simpler indicator that was OFF,ON and not BLINK,ON. He put together this circuit (requires Java) that pulses a reset pin whenever the input goes HIGH, but in this case it needs to pulse whenever the square wave stops.
I recently learned how to program an ATtiny85, so I am going to use that if no one can come up with any analog equivalent. I know it is overkill but I think this is one of the niche uses of them.