Roms with dual window feature? (LG feature thing)

Hey! Not sure if it's the correct forum, but well.

I'm looking for roms with dual window feature, as I kinda can't be without it.

This is what I mean:


(http://m.imgur.com/hWGl3fj)

Is it ONLY for LG stock roms/tweaked roms? Like Cloudy rom etc.

I really want calendar and calculator. :/

Thanks a lot for answer!