2 Macs sharing Displays via Spaces or something else? My partner and I work on iOS apps together, he's on one Mac and I'm on another. We often need to see each other's displays though and right now we have a monitor that we swap back and forth. When I want him to watch my screen, I plug the monitor into my external display port and spin the monitor around to him (and vice versa). 

Is there any way to get a video IN signal such that I could just swap to a different virtual desktop in Spaces (or something else) and see what he's doing without having to do this lame hardware swapping? 

The external monitor I have doesn't match the resolution of our Macs, so whenever we plug in to share the screen it reduces the size of our desktops and that sucks. 

Any suggestions?

Looking over the shoulder isn't an acceptable answer ;)
Screen sharing?  It does exactly what (I think) you're trying to do.
System Preferences > Sharing > Screen Sharing.  You may need to create him an account on your machine, and vice-versa.