1. A hand-held controller of the pistol-grip type with a trigger element in a trigger guard housing adapted for contact with a single finger of an operator's controlling hand, said trigger element in said housing being capable of two-degrees-of-freedom movement in response to feedback control signals applied thereto, wherein feedback-induced movement at said trigger element reflects at least a pair of controlled parameters at a unit that is being controlled by said hand-held controller, said controller comprising: a finger-sized opening in said housing adapted to receive an operator's finger with the inner surface of the finger in contact with said trigger element and the outer surface of the finger in contact with a trigger guard portion of said housing so that inward or outward movement of that finger develops an inward or an outward force on said housing; means responsive to the inward or outward force developed by the operator's finger on said trigger element or on said guard portion, respectively, for creating control signals to be emitted from said controller; means responsive to a first electrical feedback signal for controlling one degree of movement of said trigger element, which movement can be sensed by said single finger of said operator's hand, said one degree of movement comprising movement in unison of said housing and trigger element; and means responsive to a second feedback signal for controlling the other degree of movement of said trigger element within said housing, which other movement can also be sensed separately from said first-degree-of-freedom movement by the same finger of said operator's hand, said other degree of movement comprising rotation or pivoting of the trigger element independent of the housing.