A brushing tracker configured to be mounted to a toothbrush has a motion sensor and a transceiver that collect and output raw motion data. The raw motion data is received by a relay and forwarded to a cloud-based remote processing system that processes the raw motion data to determine brushing adequacy based on predetermined criteria. The motion sensor and transceiver are disposed in a flexible case. An attachment band enables the brushing tracker to be affixed to a standard toothbrush for use and affixed to a different toothbrush when desired.