Tools for Realtime Previz

VCam for Unreal Engine
This is a great tool by Epic that lets you use your phone as a virtual camera. You can create your camera moves physically, while seeing the scene on your phone screen.

Velox
A really interesting approach to bringing live action footage into Unreal. Capable of extracting and placing people or objects from footage, this could be a really quick and easy way to previsualise a virtual production shot before heading to a volume.

Simulon
Simulon uses AR to place 3D assets into the real world, where you can then film the results. Uses lighting info to better embed the augmented content. Could be useful for location scouting.