"Canabalt" helped popularize the insanely-hard-one-button-platformer genre, and made a name for its developers at Semi Secret. The tiny developer's next time, "Gravity Hook HD," is a remake of a Flash game they actually made before "Canabalt."
Like the popular platformer, "Gravity Hook" is punishingly difficult and encourages a just-one-more-game mentality. It's currently available in the New Zealand app store, and the developer anticipates it'll be out in the US at around 11PM ET for a price of $2.99. The app will be universal, so the single download will work on both the iPad and iPhone.
As an added bonus, you don't actually have to pay a dime to try it out. Hell, you don't even need to wait until later tonight, as there's a full-featured Flash version on the official site right now. Do it now!