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.
GPS Details shows you the raw GPS data reported by your iPhone. It allows you to see Latitude, Longitude and Altitude. It will also show you the currently reported horizontal accuracy and vertical accuracy.