Running 8.1.70 on Samsung Galaxy Tab 4 7.0 and Skyguard vision pro ADS-B.  
flew over 5 hours with this set up this week. 
When the Tablet toggles between onboard GPS and External Skyguard ADS-B GPS I loose lock, the unit cycles every 5 seconds or so. 
Flying within range to an ADS-B station  at 4500 feet and getting a good receive on the Skyguard from ATC ground station LAX station... I found many missing aircraft flying in close proximity to me.  The aircraft where talking to Van Nuys and were squawking, I could see them but the aircraft were not showing up on ADS-B,  don't know if this is a ground station problem or my equipment.  Other Non ADS-B traffic were on my screen but not All.  Could be that those aircraft were not getting hit by ATC radar. 
 
also I came to find out the Samsung Galaxy Tab 4 7.0 does not have a magnetometer.  Does the Ifly App use a Magnetometer?