In this paper, we propose a framework called an IoT activity tracker to ensure the safe and secure use of IoT devices around the home. The IoT activity tracker identifies the types of IoT devices and their triggering functions by traffic pattern analysis, and provides information about which IoT devices are running in the home. Also, it allows users to temporarily or permanently block the network of a particular IoT device from their smartphone if the user notices unauthorized activity of the IoT device. Furthermore, the system can be linked to sensor-based behavior recognition. For example, an IoT-based smart lock can automatically switch the communication permissions between those when the user is out and those when the user is at home depending on its status. In this paper, we report the results of a proof of concept experiment on our proposed system, which consists of a router with the proposed function and a cloud server that interfaces with users.