i made a quick video to explain how to get working brake lights on your RC for only a few bucks.
DISCLAIMER: if you dont understand basic electronics then dont try this as there is a slight risk of damaging your Rx if you dont know what your doing, but anyone who knows how to solder and tell a positive wire from a negative (red/black) should be able to do it very easily.
note: i used one LED in the video to show simple wiring, but the 47ohm resistor i used will actually power 2x 3mm LED in parallel for left/right brake lights and keep the wiring very simple with only 2 wires (pos and neg) to the rear bumper
if you run different LED's, or want to run more or less LED then use LEDCALC.com to get the correct resistor value. its not my website but i found it very handy.
see the description for more info. i suggest testing it out on an old Rx before fitting to your RC just to be safe.
2x 3mm LED (for rpm tail light kit)
47ohm 1/2 watt resistor
cheap servo - i used a micro servo as the circuit board is nice and small
Y harness, to hook it up to your ESC or throttle/brake servo on a nitro.
again i stress. if you dont have basic electronic knowledge or know what a resistor is then you shouldnt be doing it. just go buy a kit from an rc lights store.