Given a range of opponent pat hands in 2-7 lowball, it tells you how often your 1-card draw will win. The liveness of outs is taken into account. It runs entirely on the local browser.
I've only tested the fancy DHTML under Firefox; if I'm feeling sufficiently motivated I'll run IE and see what happens. But I really have no stomach for jumping through lots of hoops to make it work. (Oh, yeah, I wanted to run the XHTML validator on the page too...)