Gameloft has Brain Challenge (iTunes Link) in the iTunes App Store for $0.99 for a limited time.

Just like your body, your brain needs to exercise to stay in shape. Maintaining it simply involves completing little exercises without pain, stress, or boredom. That’s where Brain Challenge™ comes in! It’s like a real vitamin boost for your brain. More than just a game, Brain Challenge is your personal coach and an entertaining, easy solution for keeping your brain alert. For each question, simply touch or directly draw the correct answer on the screen. Enjoy turning your iPhone to arrange cubes by gravity in an additional, exclusive mini-game. With various fun exercises, train your brain whenever and wherever you want on your iPhone!