Block CEO and Twitter co-founder Jack Dorsey has launched a new app that gives users a rough idea of how much exposure they’ve had to the sun.
Dorsey shared the “Sun Day” app to his followers on X on Sunday, which, according to its white paper on GitHub, “calculates vitamin D synthesis from UV exposure using a multifactor model based on scientific research.”
Beta version available through TestFlight
It is available through Apple’s TestFlight app, which allows developers to test beta versions of their apps to get feedback from users before an official release.
The app uses location services to track the current UV index and estimate sun exposure based on the user’s location. It also asks for input on age, type of clothing being worn and individual skin tone.
It also factors in other data from the Apple Health app and historical data such as HealthKit vitamin D records.
“The app aims to provide personalized, accurate estimates while remaining conservative for safety,” its white paper states.
Sun Day requires manual input to work
The app requires a user to input data manually. Users will need to tap a button when they’re exposed to the sun and again once they are back indoors.
“[…] doesn’t look for light. It’s a manual on/off toggle,” Dorsey said in response to a user’s question on X, explaining to another that the app logs after each session.
There are also several improvements flagged for the future. The white paper lists using more precise calculations based on height and weight, along with seasonal adjustments and the user’s actual vitamin D blood tests as possible updates.
Dorsey’s second app in two weeks
Last weekend, Dorsey launched the beta version of a new decentralized peer-to-peer messaging service known as Bitchat, which runs entirely over Bluetooth.
At the time, he said his weekend was spent learning about “Bluetooth mesh networks, relays, store and forward models, message encryption models, and a few other things.”
Related: Jack Dorsey pushes Signal to adopt Bitcoin payments
In a post on Sunday, Dorsey told a user who asked if the app launches were part of a plan to flood the market and see what sticks that, “Nah. I’m learning.”
He also revealed that he was using Block’s artificial intelligence assistant, Goose, to create the apps.
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