Need a circuit design

[AdamEvenson]

I need a circuit design, a blueprint, from which I can go to Radio Shack or wherever, and buy the components necessary to construct a circuit that will somehow plug into or be hard wired into a typical, off-the-shelf pulse beat sensor (that provides a pulse beat readout of some kind), which circuit will open or close a 12 VDC switch for supplying DC voltage to an "X" device each time my heart beats. I can't/won't discuss, at this point, exactly what I will use the circuit for turning on and off with my pulse beat because my invention is in the research stage right now. If there is a company or individual that designs such circuits, I'd be happy to buy the circuit design from said company or individual, if the price is right, obviously. In other words, when my pulse beats, I want a device that will perform a special electronic duty for me that is unrelated to the pulse beat monitor itself. Let's say, just for example, that I wanted a 12 VDC bell to ring or a light to flash on and off each time my pulse beats. This is not what I want to do with it in my invention, but these are only examples of what I could do with it if I had such a circuit attached to a pulse beat monitor. I appreciate any forthcoming info.

ADDED TO ORIGINAL BY AUTHOR: I may be approaching this wrong by specifying an off-the-shelf blood pressure monitor as part of the device. Let me put it this way: what would be the simplest and easiest electronic circuit, which I could build from Radio Shack components, that would detect my heart beat (pulse) and ring a 12 VDC bell with each beat? To the first, and/or best workable design I receive, I'll award a $100 bill within 30 days (which time would give me a chance to construct it and prove it works.) I hope this doesn't violate any rule(s) of this website. If it does, I'll happily edit and try still another way that is acceptable within the rules of the website.

[pebe]

How would the sensor be attached to the user?

[AdamEvenson]

I may not need any further help. I am looking into a situation right now that may suffice. Thank you.