Help Hax0ring my Honda, please

[DanL]

<insert applause/death-threats for alliteration in subject>

Hey everybody... now that I've finished my first major computer mod (a cool-looking hdd idle / activity led mod), I want to add some LED's to my car.

I got this idea while trying to find a wiring diagram for my '98 Honda Accord to fix a minor electrical problem (not getting into that).

I found out the way the tachometer/speedometer work is by servo's, and servo's have control wires. So I was thinking... if the control wire for the tachometer is so easily accessible, shouldn't it be possible to cut into it and do something with that information?

That brings me back to my original point: LED's. Here's my idea: use the tachometer servo control wire to control two LED's. As the RPM rises from say 0 to 3x, the intensity of one LED (say blue) fades, and as the RPM rises from 2x to 5x+, the intensity of another LED (say red) increases. If these LEDs were put close to each other and perhaps a diffusion filter (ala glass frosting) was used, I would get the effect of a fade from blue to red depending on my engine's RPM.

Anyways, the reason I'm posting this here is because:
1. I don't know the specifics of the type of signal the tachometer/speedometer uses. It's a servo, so some kind of PWM, I suppose?
2. I don't know enough about electronics to create a frequency-to-voltage converter.

I did some searching, and I first found this: Idea for a Car Tachometer. The circuit here converts a car tachometer signal to an analogue voltage output. This is good. Unfortunately, this is beyond my (current) electrical comprehension.

A little more searching and I found this site. A guy at the bottom said that, "A simple RC circuit will convert a pulse train into an analogue voltage based on the frequency of the pulses. " Not knowing what a simple RC circuit was, I did some searching and came up with this guide: Understanding Signals. Capacitors and resistors, hoorj! Upon closer inspection of that PDF, I noticed it was produced by our good friends Parallax. Upon actual reading of the PDF, I realized they were using a BASIC stamp to generate and then read a frequency signal (using a Parallax computer oscilloscope device). So, that got me thinking... if I don't understand the first circuit mentioned above, can I just use a BASIC stamp to do what I want to do?

Any help would be appreciated - I know there are a lot of automobile and electrical guru's on ChiefDelphi.

As for the whole street-legal issue, psah! I don't know enough about those rules to know for certain, but I never was a fan of plain things.