Jack Dorsey Launches Sun Day Health App

Jack Dorsey, Twitter co-founder and CEO of Block, has launched Sun Day, an iOS app that tracks users' sun exposure and estimates vitamin D synthesis using factors such as location, skin type, clothing, and time in sunlight. Available in beta via Apple's TestFlight and open-sourced on GitHub, the app requires users to manually start and stop exposure sessions to provide personalized vitamin D and sunburn risk estimates. Sun Day was released shortly after Dorsey's encrypted peer-to-peer messaging app Bitchat, both developed with the help of Goose, an open-source AI coding tool. These projects underscore Dorsey's focus on personal health, privacy, and sovereign technology. The recent surge of interest in AI-assisted development platforms like Goose and Windsurf has attracted attention from major tech companies, with Google recently acquiring Windsurf's talent after OpenAI's failed bid. Sun Day continues to evolve with plans to integrate more health data and is part of Dorsey's commitment to transparency and scientific rigor.