Signpost

We have all seen those signposts - the ones stuck in the middle of nowhere with a multitude of signs pointing to famous places (London, New York, Yoko, Rowville, etc). They all point across the surface of the earth - presumably to follow a great circle to the desired locale.

I want one which points as the laser shoots. THROUGH THE EARTH! Especially from Australia, this would be pretty neat I think, with most of North America and Europe being various points DOWN.

For bonus points, instead of a signpost, make it out of actual lasers! (and sealed in a cage with appropriate gas so the line of the laser is visible)