If you need to be able to control your layout on the move or from two or more points, then handheld controllers are ideal.  Fitted with a 1.5m length of cable, these units can be used from one central control point, or alternatively can be unplugged and plugged into a different socket at a second point on the layout.  This gives a better level of flexibility and means that the user can operate from any vantage point on their layout should they wish.