By the way, DO NOT USE GV157 with iPhone7/7 Plus. It causes iPhone to reboot or causes iOS Tello app malfunction. My Tello flew away because the bug in iPhone 7/7 Plus firmware.
I am using GV157. It connect to iPhone via Lightning connector. It does work well. For the bluetooth gamepad, I think Tello channel selector is not so good. Probably it cannot switch to available channel so the wifi is interferred by bluetooth.