I flew with iOS 8.4 and app 1.2.0 today, and the app completely froze up the phone. The P3A was 1688' away and 311' up when it happened, and about 50% battery. I had just gotten the "Weak Video Transmission" warning before it happened - some trees in the way. Don't know if any of the above has anything to do with it. I used RTH to get the aircraft home. The iPhone 6+ would not even respond to the home button. I had to power down the phone and restart it, then restart the app. The aircraft was just starting to descend during the RTH when I got the app back up and FPV restored. I have the phone in a slim plastic case. A prior thread here suggested that a case could cause the phone to overheat. Ambient temperature abouit 76°F.
Didn't happen on any of my prior flights - about 15 of them.