About Nightpenny.

Nightpenny is a calm, honest sleep debt tracker for iPhone and Apple Watch. Your last 14 nights are a savings account: short nights are withdrawals, good nights are deposits, and the headline number is the running balance. Built around Pennie, a copper piggy bank who keeps the books.

The team

Nightpenny is published by Foxtaming, a one-person studio. Thomas writes every line of code, reads every support email, and is the human on the other side of contact@nightpenny.com. There is no team, no investor pressure, no growth team. Just one developer answering one question: what would a sleep tracker look like if it respected your time?

The app

• Platform: iOS 17+. Native iPhone and Apple Watch.
• Current version: 1.0.0 (published 2026-05-11).
• App Store: Nightpenny on the App Store.
• Languages: English, German, French, Japanese (App Store).

The science

Two well-studied ideas, rendered as a piggy bank:

• Borbély's two-process model (1982). Process S (homeostatic sleep pressure) climbs with every waking hour; Process C (the circadian alerting signal) oscillates over 24 hours. Their interaction is what the typical-dip heatmap visualises.
• Van Dongen et al. 2003 (Sleep 26:2). The chronic restriction study that gives Nightpenny its 14-night rolling window and the −8h debt clamp.

Full details on the methodology page, including how the Forecast heatmap is built and why the first hour of a deposit counts more.

The data posture

• HealthKit reader only. Sleep records, heart-rate variability and resting heart rate (when available) are read on-device with the user's explicit permission.
• On-device only. No CloudKit sync. No server copy. App Store §5.1.3 compliant.
• Opt-in analytics, event names only. Numbers, durations, balance values cannot leave the device — the analytics API refuses them at the type level.

Full breakdown on the privacy page.

Pricing

• Free install. Full 14-night ledger, first Sunday ritual, manual entry, weekly advice card from Pennie.
• Monthly: $3.99 USD/month.
• Annual: $34.99 USD/year, with a 14-day free trial. Family Sharing enabled.

Disclaimer

Nightpenny is not a medical device. It does not diagnose, treat, or prevent any condition. If you are concerned about your sleep, please consult a healthcare provider. See the full terms of use for the disclaimer in legal form.

Press & contact

Reviewers and journalists: see the press kit for logos, screenshots, a founder photo (when available), and brand assets. For anything else, email contact@nightpenny.com. Founder on LinkedIn.