CallBook is an Amateur Radio application that allows you to look up Ham Radio call signs via the free WM7D server, the QRZ Online subscription service or the HamCall subscription server and track active APRS stations on www.aprs.fi. Lookup results can be emailed and the QTH can be instantly viewed in the Maps application. Note: Location information is not available for all calls and is dependent on the 3rd party servers. Different parts of the world have different levels of map data detail available for display in the Maps application. In areas where there is no satellite imagery available the Maps application will show "No Images".