Need help with electronic circuit design

I need an electronic circuit that will hook into the circuitry of an off-the-shelf pulse monitor, which will turn an external, 12 VDC light bulb on and off with the rhythm of my pulse, or heartbeat. I am fairly competent with electronic components, but I don't understand electronic principles enough to design what I need here. Thanks for any input.

Can you post the spec of this off-the-shelf monitor?

I'm sorry, but I had not foreseen this possibility. I'll go looking for a spec and return when I find one. I was thinking that there may be some generic manner that I could hook into that is specific to pretty much all the units on the market. However, you have provided me with additional information that I will have to seek out a particular spec related to what I am talking about. Thanks kindly for heading me in the right direction for the present, at least.