The Scoop Free Classic Self Cleaning Litter Box from PetSafe is a good box to introduce to your cats.  The tray was easy to install and the instructions are easy to follow.  This enables me to "scoop" less frequently, but the box takes care of it for you.  Great if I need to leave for an extended day's hours.  The solids are scooped to be collected, and the liquids are redistributed by the crystals.  As with clay litter, the crystals do get a bit of traction outside of the box.  Can set for automatic or manual raking as well.