Our friends at ICTP in Italy are presenting a global effort to record TV White Spaces in a worldwide database. These are RF frequencies formerly allocated by TV broadcast but not actually used. By detecting these whitespaces certain licensed and unlicensed transmissions can benefit from it. This project is using RFTrack Android app and a connected RF Explorer to capture GPS & RF activity, then uploaded to a global repository.
And this is all offered for free. As a community we can benefit from a global database with this information being timely updated. Contributors are appreciated: all you need is a RF Explorer and an Android device, record data from your local city and upload into the database.
The ICTP TVWS global database is available on this link: wireless.ictp.it/tvws/