Visually representing enemy cone of vision without Unity Pro?

edit: I should mention that I’m doing this in Unity 4.
I’m working on a top down shooter in which the player will try to avoid being spotted by the guards. edit: the guards walk around and chase after the player if they spot him. I have successfully coded the guards’ vision so they spot the player correctly, but I’m having trouble accurately representing the guards’ vision to the player. My idea was to have a spotlight attached to the guard that has the same range and angle as his view. The problem is without Unity Pro, I can’t do shadows or deferred lighting. Does anyone have any suggestions? It actually wouldn’t be the end of the world if I needed to give up on visible lines of sight, the game is shaping up to be more of a shooter than a stealth game anyway. I just want to see if I’ve missed something pretty straightforward that could get the job done. Thanks!

Spotlight shining through wall

In the unity stealth tutorial they do something similar with CCTV cameras
each camera has a “vision cone” represented by a custom shape with a collider.

then they use a spotlight to represent the area of vision on the ground.
but i think you can also adjust the collider object to look as if the area is dangerous.

With Unity 5 you don’t need Pro to do what you want anymore.