The download button opens the iTunes App Store, where you
may continue the download process. You must have iTunes installed with an
active iTunes account in order to download and install the software. This
download may not be available in some countries.
From Geoverlay Ltd.:
Place a text message at your current location. View the text message through a special camera feed when you are within 10 metres of it.Search for messages that you've already placed which are further away using the Geoverlay Radar.