A lot of people buy Nintendo DSes for the sole purpose of having those Dr. Kawashima-approved brain-training games at hand. With this app, you get the exact same mind-juicing benefits for a few bucks, on hardware you already carry.
You can debate the long-term efficacy of brain training games all you want, but there's no denying that a few quick puzzles in the morning help jolt you awake, and at least make you feel a little sharper. Anyone who's used a prior Kawashima game will take to this one instantly, and any exercises that've been taken out on account of the iPhone's lack of stylus have been replaced with something equally clever.
Lite: Free, Full: $5
From the App Developers: The original and best brain training game is now available for iPhone™ and iPod touch®. You can play the Brain Training game supervised by Dr. Kawashima.