Abstract: A product interaction monitor includes sensors for measuring characteristics related to the product and/or product package or other type of container. The product interaction monitor can be installed in a container cap and used to monitor events associated with the container such as product usage. The product interaction monitor can utilize multiple sensor outputs to increase the accuracy of the detection of the events. The product interaction monitor can be used to estimate product inventory or product usage and communicate information regarding the product and/or product usage to a local display or a remote computer.