i3* does that. You specify a set of workspaces and their screens. Personally I go a step further and set programs to specific workspaces as well.
This works really nice with a docked/undocked setup. When the additional monitors are disconnected, all workspaces move to the main(laptop) display.
eg, I have workspaces 1,2,5,9 on monitor 1 and screens 3,4,6,7,8,10 on monitor 2. When undocked all 10 workspaces move to the laptop screen.