hahaha, I know what ur talking about
I did a project in college where I had to recognize a smoke detector sound (4khz) in order to start an autonomous robot electrically.
http://www.national.com/mpf/LM/LM2917.html This is a frequency to voltage conversion IC. essentially you can get it to output a voltage that is in reference to the frequency it is "seeing". you can put a couple bandpass filters on the input, that only pass certain frequencies to avoid false readings. Then by using a couple of comparators on the output, they would be able to run a transistor/mosfet in order to complete the respective circuit once the correct threshold voltage is outputed by the LM2917.
Do you have any formal education with electronix? If you are a hobby level electrician, and the description above doesnt scare you, probably we could get you up and running, but it will require some work, espeacially on ur end.