Leviton makes a 2 button/2 relay switch that works differently than SmartThings expects. Each button associates as a separate Z-Wave switch (theres a remote control that is also associated, but It seems to be less useful). The switches respond to SmartThings commands as you would expect, but pressing the physical buttons does not send standard on-off commands. Instead it sends scene commands.
I created a device type that interprets these scene commands as state changes so the buttons work like instant status updates.
The device type is available here: