I saw this on some beauty blog AGES ago (so alas I can't link) and was determined to get it, so I searched high and low (ie, ebay) to find it. Annoyingly it only comes in this red colour or a navy-ish blue. The basic premise of it is that you paint it on, then hold a magnet (that comes with the polish) over the wet paint, which causes metal bits in it to arrange themselves into a star shape.
It's pretty cool but it is SO HARD to do the magnet thing!! You have to hold the magnet riiight over the nail, and keep it totally still for 30 seconds or so. The biggest problem I found was that the polish draws itself upwards to the magnet and sticks to it like some lame cousin of the T1000 from Terminator 2.
All in all, it's a nice novelty, but it's very hard to do well, and even when you do do it well, it's too subtle to really wow anyone, so what's the point in all that effort