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 HashBang Technologies:
SmartPop listens to the popcorn in your microwave, counts the number of popped kernels, and tells you when to take it out. Several bags of popcorn were harmed in the making of this app. We've always wondered just how smart the "popcorn" button was on our microwaves. We decided to build SmartPop to be our substitute for the microwave's own "popcorn" button. We only have so many microwaves to try it on, so now we need your help! Give SmartPop a try, and leave us some feedback via email at firstname.lastname@example.org. You email us, we make SmartPop better! While you're at it, stop by our website at www.WhatIsHashBang.com for more information on our company.