I would like to suggest that the user is able to configure fongo so:
1. it would prompt the user to drop a call while on poor wifi coverage and restart the call over cellular
2. it would automatically redial a number over cellular if the call has dropped over wifi
Use case, call starts at home over wifi, user jumps into his car and drives away. Today, the call quality deteriorates and then drops (or user hangs up because of poor quality).