Ok, this is kind of cool. It's a custom keyboard for chemical formulas that makes a lot of sense. I like the quick slide down for subscript. You don't need to slide all the way over to the sub- or superscript key, just slide up or down to select.
$3 in the App Store. I bought it just to be able to paste proper molecular formulas in emails. The Wikipedia search is cute but not terribly useful.
By way of Clark Goble