More likely you d use a camera in the ceiling and probably want to process it with opencv.
Floor reflection unity.
I like this opencv asset for unity.
The effect descriptions on this page refer to the default effects found within the post processing stack.
More info see in glossary window that are used for editing the size and probe origin properties directly within the scene.
There are two buttons at the top of the reflection probe inspector a unity window that displays information about the currently selected gameobject asset or project settings alowing you to inspect and edit the values.
You can probably use this for more things like wall mirrors and multiple reflections in the same scene but that would require quite a bit more scripting magic.
It is commonly used to create more subtle reflections such as on wet floor surfaces or in puddles.
With the leftmost button size selected.
Now i did realize that unity free has reflection probes.
From my understanding you create a material push the smoothness to 1 and then place a reflection probe in the scene and all the materials smooth enough.
Here s a quick tutorial on how to create realtime reflections in unity 5.
This approach is very hacky but you can use the new reflection probes in unity 5 to easily create realtime reflections for something like a reflective floor.
It may be possible to get some sort of sensors in the floor and then you re doing entirely custom things to read the data.