is there an iphone app that allows one to link phone and pc use the phone as a viewer (using pc keyboard for navigation) for Unreal Builds?
A VNC Viewer is what comes to mind: http://www.148apps.com/reviews/vnc-viewer-review/
There’s a bunch of them out there, so you’ll have to do some research 
I am talking about using the iphone’s gyro. Not talking about monitoring my desktop. I can do that with team viewer.
Your question failed to mention that.
I only know of this for the UDK -http://udn.epicgames.com/Three/UDKRemote.html. I heard of this working in UE4 but I’ve never seen it. There are some threads about it on the forums