Facial Detection Out Of Mobile Video Stream

Has anybody done any work around detecting faces (not recognizing) in a video stream from iOS or Android? Does the mobile SDKs have anything built into them or would you have to use a deep learning model or similar to run over the video stream once captured on the UE4 side?

This seems to be ideal: GitHub - rnixik/face-recognition-ue4: C++ project for face recognition with OpenCV which compiles into native library for Android and works from UE4 project

that seem to be a recognition algorithm. I simply want to detect faces and locations and was hoping there would be native functionality in Android or iOS to use for that?