engine running indicator

I'm looking for a way to energize a relay when the engine of my Ford F150 is running.  The relay would need to drop out when the engine is turned off.   I'm  wanting to operate lights, etc while running only.

buy a latching relay module (cant rember name) or build one, use the starter to latch it and the ignition to break contact (might be a problem if you car dosent start on the first try).  the other idea im having is to use the *55020 speaker to rca module*(the ones that turn speaker out put in remote turn on) and hook that up to a solid tach source.  i have never used either of these methods to do what your attempting to do, but im pretty sure one or the other would work.

ps. personaly would try the 55020 module first see if it works since it's the least laborious of the two.

Not familiar with the 55020.   The truck has a charging indicator on the instrument cluster.   I've thought about looking for that wire or fuse.   This is on while engine is running.   Any comments?

No luck yet.   Hasn't anyone done this before??   

I'm looking for a +12V output while the engine is running.   This could be used for all kinds of light displays, etc.    But only while in run.

Do a google search for frequency switch.  You can wire a frequency switch up to a fuel injector (very similar to the idea above).

Thanks very much!!!!

Found it at autospeed.com   Looks like they have a kit that'l do exactly what I want.

Again - Thanks for the info

On second thought ---   Since the above kit comes from Australia ---  Think I'll wire up a circuit like the dual relay driver board on www.anykits.com .   It only needs 2-5 volts input to operate.    I can get this voltage from a tach source (after it is filtered)on the engine.   Much simpler anyway