The talk is about the implementation of the Google and Apple Exposure Notification Protocol called the Contact Tracing API. The speaker discusses their personal project to create an open-source implementation of the protocol for their operating system called Selfish OS. They explain how the protocol works, its privacy-focused features, and the challenges they faced in working with Google, Apple, and the team behind the COVID-WARN app in Germany. Overall, they found the specifications and APIs provided by Google and Apple to be high-quality, but they had zero engagement with them. On the other hand, the team behind the COVID-WARN app was committed to openness and provided a lot of code and documentation, but they were overwhelmed and took too long to integrate fixes and changes suggested by independent developers. The speaker concludes that there is room for improvement in terms of collaboration and communication between large tech companies and independent developers working on open-source projects.