Been looking at different ways to mod the little details in the car, saw a couple of pictures of one member here with his foot wells led'd and wired to the rcl so they lit up when the doors are unlocked/locked and when theyre open? Thinking about doing this, but i was also intrigued by 'sound activated leds' which i found was rather more of the 'show off' type lighting. Mind, I wouldnt mind some thing like a small dim red light going off to my music!
Would they be illegal? Just researching on youtube where yanks have done this sort of mod.

link is here

As I am actually planning a boot build for my car, I thought i may as well put the effort in and add some lights!

Could anyone hit me up with opinions? Ideas etc?