This paper describes a recreational-activity monitoring system that records the existence of tools (removed or not from a predefined place) that are used in the recreation activities. The system is composed of three types (infrared, ultrasonic, and RFID) of proximity sensors to adapt to various sizes of the target object. The timings of when the target object was removed and returned are monitored. Simple experiments showed that the detectable range of the system was approximately 60 approximately 100 mm, and concluded that the infrared and ultrasonic sensors were useful for relatively large objects, and the RFID technology was suitable for small objects.