help configure 2 Macs. KVM solution?

2012 iMac, Mavericks
2014 macbook Air, Yosemite

I have an iMac work station with a secondary HP Dream Color monitor hooked up DVI-D or VGA. Wired Mouse, wired keyboard, headphones.

I want to monitor my Air on that secondary monitor. I'd like to also work on my System A but monitor system B while I work.
So this may be some type of independent switch?
Not sure just starting to hash this out. Any ideas?
Thanks in advanced.

 

That is an interesting idea.

How would I work on System A while monitoring and listening to System B? Is that possible?

I suppose I would drag the shared screen over to the secondary monitor? Do I hard wire this together

System A is not on any network for security.
Thanks for the idea.