Name: Nifty Sleep Tracker
Rating: 2 (1 reviews)
Author: CelestialFire

Track Your Sleep Stages Throughout the Night:
Nifty Sleep Tracker is a simple, yet sophisticated sleep tracker app for your Garmin Watch. I wanted to create a sleep tracking app where I could view stats on my watch—both nightly results as well as best and average values over time. However, Garmin doesn't provide access to sleep data values through the general API. Therefore, creating a sleep tracker app requires building your own using sensor data.

Important: The data reported in Nifty Sleep Tracker—such as sleep score and sleep classification percentages—will not match Garmin's built-in values. Overall, Nifty Sleep Tracker is more stringent than Garmin's scoring. While other values come close to Garmin's, they won't be perfect. That said, I wasn't attempting to replicate Garmin exactly. Instead, I wanted a fun detection and classification algorithm that provides additional insights into your sleep patterns. Please note: this is not a medical-grade app. It's designed to give users fun, useful insights into their sleep.

While the app is meant to be fun, I want to acknowledge the significant work behind it. It took me a month to iron out bugs and quirks, and there may be more I haven't discovered yet. Updates will continue as development progresses. I chose a price point that reflects my time and effort fairly—not every app can be free, especially one requiring dozens of hours to reach a working version.

If you encounter issues (crashes or unexpected behavior), please contact me so I can troubleshoot. There's a Raw Data View that displays diagnostic information I can use to help resolve problems.

How It Works:
SleepTracker uses five key signals from your watch to estimate your sleep stages:

1. Heart Rate:
Monitors your heart rate throughout the night
Recognizes that different sleep stages have distinct heart rate patterns
Adapts to your personal resting heart rate for accuracy

2. Movement:
Tracks motion using your watch's accelerometer
Deep sleep typically shows minimal movement
REM and light sleep usually involve more tossing and turning

3. Sleep Consistency:
Analyzes heart rate stability throughout the night
Stable patterns often indicate deeper, more restful sleep
Variable patterns might suggest lighter sleep or disruptions

4. Stress Values:
Your stress metric is analyzed during the detection window
Both stress averages and variance support sleep detection and classification

5. Body Battery Values:
Body Battery metrics are used during the sleep detection window
Provides insight into your recovery and sleep quality
The app combines these signals to estimate your sleep stage at any moment, tracks sleep throughout the night, and gives you a complete breakdown in the morning.

Settings Changes:
Prior to version 3.6.0, the user would select their resting HR directly in the IQ settings for the app. However, this required the user to be certain of their resting HR, and overall the calculations for detection and classification were decent but in some ways limited.

Going forward, the resting HR setting has been replaced in version 3.6.0+. Now, there will be three new settings:

User Age – This is the main setting that provides the starting point for determining a resting HR value for the person. The main driving force behind the calculation comes from a max theoretical HR, and taking a base of the value. In this case, 28% of max HR is used as the base value.

Tuning Value – Has a selectable range of 1–7, but is defaulted to 3. The user can change this value if they feel their results are not exactly accurate. The higher the value, the more sensitive to sleep the app will be during the set sleep window. 

Athletic Ability – Finally, there is a setting for athletic ability the user can choose from. There are four options: Basic, Intermediate, Advanced, and Professional Athlete.