The "Download Now" link directs you to the iTunes App Store, where you must continue the download process. You must have iTunes installed in order to open the link, and you must have an active iTunes account to download the application. This download may not be available in some countries.
From Dream Injector:
Admit it, you're always thought you were the smartest person in the room. Now you can confirm your suspicions with Brain Scan.Brain Scan uses the phones built-in microphone and speaker as a type of radar to capture depth and distance information about the scanning subject. This data along with cues from the gyroscope and proximity sensor are used to create a stereoscopic brain survey of the subject. This brain survey is the basis for the Brain Scan results which shows brain dimensions, activity and a probably IQ. Okay, maybe the app doesn't really do all that... but it looks like it does, and that is the fun part after all.You can secretly preselect what size brain you want the scan to reveal which leads to all sorts of tomfoolery. It's all explained on the about screen... which you can hide once you learn the trick so nobody will know the secret. Who's the smart one now? You are if you download the Brain Scan. Best of all Brain Scan is free. You'd have to be a dullard not to give it a try.