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 Simplysoft GmbH:
Use your iPhone or iPad and let your Passbook passes show up on devices near you. This app uses the new iBeacon feature in iOS 7 to broadcast your presence using Bluetooth LE. Passbook passes that uses this new iBeacon feature will show up on the lock screen of a device that is inside your region. With this app you can manage multiple such regions (proximity UUIDs), you can either use your own region or use predefined regions of Passbook service providers This app is only compatible with devices that support Bluetooth LE