synchronize multiple monitor

I know this is a few months old but just in case someone else is still looking, here are some solutions to look into.

I believe you are talking about a host and IG simulation type setup with 3 computers to run the 3 screens. I was able to achieve this using a combination of hardware and networking. I used an nvidia card with spanning mode to create the front view of a ships bridge across three 60 inch TVs. Then used networking to connect another PC with two more 60 inch TVs to create the side view of the bridge. This gave you a wrap around feeling of being on the bridge running from two PCs.

You could achieve the same affect by running three PCs with a single monitor and using Unity's networking. You would update the ships position on the server computer then use networking to update the two client computers. You would have to worry about camera viewpoints overlapping and making sure you updated all the required states across the machines.

Another option depending on what your project is for would be to look into Unity's cluster rendering. This is setup to handle that Host IG simulation scenario for you but requires a separate license. Cluster rending didn't exist when I created my system but I am going to revisit it once I get a license.

http://docs.unity3d.com/Manual/Clusters.html

http://unity3d.com/learn/resources/talks/cluster-rendering-tech-preview