Sergey Chernyshev presented Show Slow, a tool he developed for keeping track of website performance. Show Slow allows automated monitoring and collection of performance metrics over time to identify issues. It works by running tests on websites using tools like YSlow and PageSpeed and sending the collected data to a Show Slow instance for analysis, ranking, and debugging. Sergey demonstrated Show Slow and invited attendees to provide feedback, get involved in the open source project, or contact him directly for more information.