A bicycle trailer brake includes an actuator forming a lever to actuate a brake. The actuator includes a mounting structure to couple the actuator to a bicycle or bicycle trailer and an input interface to receive an input force from a user. Upon attachment of the mounting structure to a bicycle or bicycle trailer, the input interface is positioned in a position behind and above a bicycle seat of a bicycle.

Certain embodiments provide a head array system for a power wheelchair, including a head array body and one or more lateral arms. The head array body includes shafts. Each of the shafts includes lateral arm receiving sections. The one or more lateral arms are detachably coupled to one of the lateral arm receiving sections of one of the shafts.

Certain embodiments provide a head array system for a power wheelchair, including a head array body and one or more lateral arms. The head array body includes shafts. Each of the shafts includes lateral arm receiving sections. The one or more lateral arms are detachably coupled to one of the lateral arm receiving sections of one of the shafts.

Implementations relate to a master control device. In some implementations, a master control device includes a thumb grip member including a thumb grip receptive to a thumb of a hand of a user. The master control device includes a finger grip member coupled to the thumb grip member at a proximal end of the master control device and extending toward a distal end of the master control device, where the finger grip member includes a finger grip receptive to multiple fingers of the hand. The thumb grip member and finger grip member are movable in a pinching configuration with respect to each other. The master control device includes a sensor coupled to at least one of the thumb grip member or finger grip member to sense relative positions of the thumb grip member and finger grip member with respect to each other in the pinching configuration.