Apparatus, systems, and methods for monitoring head acceleration and/or forces acting thereon are disclosed. A device for monitoring an acceleration or a force acting on the head of a user includes a flexible article adapted to be worn on the head of the user; and a monitoring assembly coupled to the flexible article. The monitoring assembly includes a sensor for measuring a force on the head and transmitting data relating to the force, the sensor disposed proximate to the head, a processor adapted to receive the force data from the sensor, and a flexible strip operatively connecting the sensor and the processor.