After Launching WhatsApp Messaging Rival, Jack Dorsey Releases New App That Tracks Sun Exposure

• Twitter co-founder, Jack Dorsey, has released a new app that tracks sun exposure and vitamin D intake
• The new app is already available on TestFlight on iOS, and its code is also on the open-source platform, GitHub, for cloning
• The new app shows users the UV intake for their location along with details like cloud cover, sunrise, and sunset timings.

Legit.ng’s Pascal Oparada has reported on tech, energy, stocks, investment and the economy for over a decade.

Jack Dorsey, Twitter co-founder, has released a new app.

After launching Bitchat, a bluetooth-based messaging app earlier this month, Dorsey unveiled a new app called Sun Day that helps users track Ultraviolet (UV) exposure and vitamin D intake.

Jack Dorsey releases Sun Day for testing

The new app is already available on TestFlight on iOS, and its code is also on the open-source platform, GitHub, for cloning.

TechCrunch reported that, like other developers, Dorsey is using the vibe-coding platform.

However, instead of using Cursor, Claude Code, or Windsurf, Dorsey says he is using an open-source coding tool called Goose.

How does the new app work?

According to reports, Sun Day is simple to use. It shows users the UV intake for their location along with details like cloud cover, sunrise, and sunset timings.

Users can choose their skin type from six options, and what kind of clothing they are wearing.

Based on the parameters, the app will calculate how long a user can expose their skin to sunlight before it starts to burn.

How does it calculate vitamin D intake?

It also shows users their minimum vitamin D intake.

They can start a session by tapping on the Track UV exposure button, and after the session ends, the app will show them how much vitamin D they have gained throughout the session and for the day.

Dorsey launches WhatsApp rival

The development comes after the Block CEO unveiled the disruptor Bluetooth messaging app, Bitchat.

Dorsey announced on Sunday, July 6, 2025, that the beta version is live with a full white paper available on GitHub.

How does Bitchat work?

Dorsey announced in a post on X on Sunday, July 6, 2025, that the new app is a personal experiment in Bluetooth mesh networks, relays and store, and store-and-forward models, message encryption, and a few other things.

According to him, Bitchat enables ephemeral, encrypted communication between nearby devices.

No Wi-fi or cell signal

CNBC reported that as users move through physical space, their phones form local bluetooth clusters and pass messages from device to device, allowing them to reach peers beyond standard range, even without Wi-Fi or cell signals.

Dorsey disclosed that bridge devices connect to overlapping clusters, increasing the mesh across greater distances.

Messages are stored only on devices, disappear by default and never touch centralised infrastructure, showing Dorsey’s push for privacy-preserving censorship-resistant communication, experts say.

How are messages sent?

Bitchat’s launch builds on his support for Damus and Bluesky and reflects a broader campaign to decentralise everything from social media to payments.

Bitchat is designed to keep working when the internet is blocked, offering a censorship-resistant way to stay connected during outages, shutdowns or surveillance.

The new app also supports optional group chats, or rooms, which can be named with hashtags and protected by passwords.

Meta introduces per-message billing for WhatsApp

Legit.ng earlier reported that the world’s most popular messaging platform, WhatsApp, commenced a per-message billing system for businesses using the platform, starting July 1, 2025.

The move is a major departure from how the messaging app monetises its business communication.

Previously, businesses were charged for a 24-hour conversation window, regardless of how many marketing messages were exchanged.

Proofreading by Funmilayo Aremu, copy editor at Legit.ng.

Source: Legit.ng