Automobile turn signal isolated circuit

[kansasspyder5]

How many out there have hearing problems? Can you suggest a way to add heads up display to a noisy sports car? Old sports car I am constructing uses one light bulb [on each side, at the rear] to indicate 1. turnsignal 2. braking 3. nighttime driving. I figure, if I can create a separated circuit to pick up fluctuating current on and current off, I can use this sensor to light a bulb nearer to my field of view.
My idea on capturing fluctuating turnsignal is to put a coil in the existing circuit to make a fluctuating magnetic field. This would induce a current in an intertwined coil. That would be one level of isolation. Second, the output of the second coil would enter a relay to switch on and off a light in my field of view.
Will this work? what type of coils would i need. what type of relay would I use [momentary to momentary?]

 

[Tom.G]

The simplest way is connect a low power light bulb between the two lights on the rear of the car.

----L-----------B----------R----

Where 'L' and 'R' are the existing brake lights and 'B' is your new indicator light. 'B' will be off when both brake lights are either On or Off. When turn signal (one brake light) is on, 'B' will be on, blinking with the turn signal. If 'B' operates when one turn signal is blinking but not when the other turn signal is blinking, then one of the rear light bulbs is burned out.

The reason for making 'B' a low power bulb is so it does not draw enough current to light the Off turn signal.

Cheers,
Tom