A handheld system includes a motion-generating mechanism having a first motor mounted to a housing to generate a first rotary motion and a second motor coupled to a first output of the first motor such that the first rotary motion imparts to the second motor and rotates the second motor within the housing. The second motor generates a second rotary motion. An attachment arm extends out of the housing and has a first end coupled to a second output of the second motor and a second end configured to attach a user assistive device. A motion sensor senses a motion of the handheld system and generates a signal in response. A control system is coupled to receive the signal and to control the first and second rotary motions with commands generated based at least in part upon the signal. The commands direct the motion-generating mechanism to stabilize unintentional muscle movements.