The present invention relates to systems that allow users to observe the operation of pool skimmers. In some embodiments, the system includes a flow sensor system, which may be located in a ring above the skimmer basket. The flow sensor system may include, for example a microphone or a paddle wheel. Optionally, the system may further include a remote computer (e.g., smart phone/tablet computer) that receives the inputs measured by the flow sensor system and displays on its display screen alerts based on the inputs (e.g., to notify the user to clean the skimmer basket or backwash the filter).