I thought the app was supposed to electronically notify the nearby towers with merely the click of a button. I could be wrong, but I do know that was the original intent when the idea was first introduced.
From the FAA's introductory supporting statement on the B4UFLY app ground at
http://www.reginfo.gov/public/do/DownloadDocument?objectID=58104500 :
3. Extent of automated information collection.
Frequent calls to an air traffic control tower would disrupt tower activities to such a degree that the FAA anticipates may endanger the safety of the National Airspace System. Therefore, the FAA has developed the B4UFLY app to facilitate a process for electronic notification, thereby reducing the time burden on both users and FAA personnel.
This data collection would be 100% electronic and automated for the user. The user will be able to quickly tap multiple choice options, and the B4UFLY app automatically pulls the user’s location from their smartphone.