Mine is charging my Iphone 7 plus. First time out with the P4 and my phone was 77%, when I was done flying my phone was 100%. But it took the controller down to 80% (2 1/2 batteries). I did much better with PsP. It's cool just would like a choice to turn on and off in case your flying somewhere where you can't let the RC drain down so fast.
There must be a setting in the go app that I'm not seeing. A buddy of mine went out flying our phantoms and when we were done my iPhone 6 Plus had a small percentage of battery left and my friends iPhone 6 was at 100% so obviously his was charging. It would be a nice feature in case your phone for whatever reason drops down too low. If anybody knows where that setting is or what the variable is on why one phone was charging one wasn't, please post.