I have occasionally thought of getting a couple of laser squares. Can't find my favorite tutorial on how to use these (work great for blocking a show quilt!), but here is a websites that shows how they are used:
http://cowtownquilts.com/tag/laser-square/ (scroll down)
Edit: Hmmm... Just found this one on Amazon and it's not too expensive. Might get one to try out. Reading the reviews, though, I will want to check it for accuracy against other squares in case it needs to be returned. At least returning items to Amazon for reason is easy. Here is the link:
http://www.amazon.com/Bosch-GTL2-Las...pr_product_top