If you thought Asus was the only company out there with a solution for external graphics cards for your notebook, think again. Magma has two products, although only one of them is likely to actually be able to accommodate a graphics cards. The Magma ExpressBox and Magma ExpressBox Pro are two external boxes that will take work in conjunction with an Express Card that slots into your notebooks Express Card slot or via an internal x1 PCI Express card in your PC. Although these solutions only work with single slot, sub 55W graphics cards that don't require an external power connector, so it's a slightly more limited solution than the XG station from Asus.
However, Magma is promising a tailor made solution for graphics cards that should make an appearance later this year. The biggest downside to either of these products is the steep price point, US$ 729 and $749 respectively, not exactly what you'd call cheap as you have to add the cost of whatever you want to put inside the box as well.
Have a look at Magma's product page for more information