Creating overlays over the world environment

Hello everyone,
i’m looking for a guidance, on how to create overlays over the existing environment
(This is an example: http://videogamewriters.com/wp-content/uploads/2012/09/2KGMKT_XCOMEU_SCREENS_PCUI_Move_02.jpg )
I understand, that you can use mesh for the cursor (already doing this), but for the other stuff (shields on walls, or overlay on the floor), how do you do this kind of stuff?

No code needed, just high-level guidance.

You should try the new 4.6 beta version of unity. It’s out now and it contains the new GUI system that will be included in Unity 5. With this new system you can easily achieve that. Have a look here: Unity 4.6 - New UI System Overview

You can easily get teh shields if you take every tile that is inside the movement radius, check if it’s neighbors provide cover, and instantiate the corresponding shield mesh at the position.