Thank you for the comments everybody! 
Armageddon, we are simply using a scene buffer (ie. a render texture) at 640x400 resolution. Then you can scale that up to whatever the game is actually running at with nearest neighbor as opposed to bi-/linear filtering and voila!

Armageddon, we are simply using a scene buffer (ie. a render texture) at 640x400 resolution. Then you can scale that up to whatever the game is actually running at with nearest neighbor as opposed to bi-/linear filtering and voila!