I purchased this controller and it works great. It even has the removable/adjustable phone holder for when I play my emulator games.

I've been using a Sminiker (Red Samurai knock off) since February. Still going strong through every Gear vr, Cardboard, or regular Android game I've thrown at it on S5 & S7Edge. Not perfect but not bad for $20

https://www.amazon.com/gp/aw/d/B00XMT025O/ref=mp_s_a_1_1?ie=UTF8&qid=1479212631&sr=8-1&pi=SY200_QL40&keywords=sminiker+controller&dpPl=1&dpID=51veTOfX3oL&ref=plSrch

I used this with a Gs5 on cardboard, and now with my s7 edge and Gear vr. I have to pair it just about every time I use it, which is annoying. But it works 100% and is iOS compatible. Comes with a phone holder and it's shaped like a ps3 controller for those who hate xBox controllers. Similar to the Red Samurai. Get it delivered by tomorrow if you have Amazon Prime.

https://www.amazon.com/gp/aw/d/B00XMT025O/ref=mp_s_a_1_1?qid=1459653207&sr=8-1&pi=SY200_QL40&keywords=sminiker+gamepad&dpPl=1&dpID=516pV1rpCUL&ref=plSrch#

This one works like a charm for my Gear VR. $21. Sminiker® Android Wireless Bluetooth Gamepad Game Controller https://www.amazon.com/dp/B00XMT025O/ref=cm_sw_r_other_awd_xUP2wbTCEMCCJ