Neon lights can be installed inside the car too. Actually its not really neon lights lar...
Have u guys seen the 'neon' lights inside the CPU of a computer, those that will flash with the bass. U can modify it and install it inside ur car...it will follow ur music bass.
It actually run on 13V current...but 12V is still able to run it. Jz find the wire of the switch to headlights and rewire it to the 'neon' and tat will do. Whenever u switch on ur headlights the neon inside ur car will follow.
I personally feel that neon inside the car wud looks better although outside ppl cant see lar..don u think those wif underglow neon looks alot like ah beng's car. NO offence yea...jz my 2cents.