Jack Dorsey Launches Sun Day App for Personalized UV Exposure Tracking

Block CEO and Twitter co-founder Jack Dorsey has introduced a new app that provides users with an estimate of their sun exposure. The app, named "Sun Day," was shared with Dorsey's followers on X and is designed to calculate vitamin D synthesis from UV exposure using a multifactor model based on scientific research. The app is currently available in its beta version through Apple’s TestFlight, which allows developers to gather user feedback before an official release.

The Sun Day app utilizes location services to track the current UV index and estimate sun exposure based on the user’s location. It also requires users to input additional data, such as age, type of clothing worn, and individual skin tone. The app integrates data from the Apple Health app and historical records, such as HealthKit vitamin D records, to provide personalized and accurate estimates while prioritizing safety.

To function, the app requires manual input from users. Users must tap a button when they are exposed to the sun and again when they return indoors. This manual on/off toggle ensures that the app logs each session accurately. Dorsey has highlighted several potential improvements for future updates, including more precise calculations based on height and weight, seasonal adjustments, and the integration of actual vitamin D blood test results.

This launch marks Dorsey's second app release in two weeks. Previously, he introduced Bitchat, a decentralized peer-to-peer messaging service that operates entirely over Bluetooth. Dorsey has been actively learning about various technologies, including Bluetooth mesh networks, relays, store and forward models, and message encryption models, which have influenced the development of his recent apps. He has also revealed that he is using Block’s artificial intelligence assistant, Goose, to create these applications.

Dorsey's new app reflects his ongoing interest in decentralization and user empowerment, themes that have been central to his previous ventures. The Sun Day app's unique concept and Dorsey's reputation as an innovator have sparked discussions about the potential applications of such technology in health and environmental monitoring. The app's launch has generated considerable interest and speculation about its future impact, highlighting Dorsey's continued influence in the tech industry.