Track your caffeine like your body actually processes it.
HalfLife is a real-time caffeine tracker for Pebble that simulates how caffeine is absorbed, peaks, and wears off — so you can stay energized, avoid crashes, and sleep better.
Note: This is a mathematical model, not medical advice.
> Why It’s Different
Most apps just estimate. HalfLife simulates using a pharmacokinetic model, it tracks your caffeine levels continuously — so you always know where you stand, not just what you drank.
> What You Get
- Real-time caffeine levels: updates every second — no static estimates.
- Peak prediction: see when your caffeine will hit hardest — and how strong it’ll be.
- Smart sleep guidance: know when your levels are low enough for quality sleep.
- 6 Custom drink presets: save your go-to coffee, tea, or energy drinks.
- Flexible drinking durations: 3 presets of 5 to 120 minutes
- Preferred caffeine range: Stay in your ideal focus zone at a glance.
- Free-form logging: enter any caffeine amount anytime.
> Built Around You
Everyone processes caffeine differently. HalfLife lets you adjust:
- Caffeine half-life (how fast it leaves your body)
- Absorption speed (how fast it gets absorbed into your bloodstream)
- Your personal sleep threshold
- Your preferred caffeine range (color display watches only)
- Or just use the built-in defaults and go.
> Real-World Uses
- Time your morning coffee for peak focus
- Avoid the afternoon crash
- Don’t ruin your sleep with late caffeine
- Plan pre-workout energy boosts
- Understand how multiple drinks stack over time
> Private & Efficient
- 100% on-device – your data never leaves your watch
- No background drain – zero battery impact when closed
- Open source – transparent and customizable
> Coming Soon
The core model is solid, but I still have some exciting plans for the future:
- Redesigned UI: A visual "glow-up" is the top priority, including support for round Pebble watches. (Already making minor progress, but I'm a bioinformatician, not a designer — so bear with me.).
- Edit active drinks: In case you set the wrong amount or duration, this feature will allow you to edit and delete your current drinks.
- Shake For Help: Shake the watch on any screen of the app for a guide on the controls and meaning of values. (With an option to disable this if you already know what's what).
- On-watch configuration: Configure most settings without needing to grab your phone.
- “Preview before you drink” feature: See how a drink will affect your levels before you log it.
- Drink planning: Plan you day's caffeine for workouts, productivity or to regulate your levels in advance. Get notifications for the drinks you scheduled when viewing the caffeine graph across 12-72 hours.
- Closed-Loop Model: When the new Pebble hardware arrives, the plan is to use advanced heart rate (specifically HRV) data to create a self-tuning model that adapts to your body's unique response. This allows for a broad array of additional features.
Note: Values in screenshots have been tampered with to show off the features.
Have a feature idea or found a bug? The code is open and contributions are always welcome! (Also some extra details on the model coming soon for the science nerds)
https://github.com/FPuzeras/HalfLife