Health Data Server vs Understanding Sleep
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
Health Data Server
Stream real-time health data from your Apple Watch to your overlay. Display heart rate, calories, and more with customizable animations and sounds. Save workout data to Apple Health.
- Stream heart rate from Apple Watch
- Display calories burned
- Customizable overlay appearance
- Heartbeat animation and sound
- Save workout data to Apple Health
- Access extensive HealthKit data
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The watch app requires watchOS 8+ This app was built to get heart rate, calories, and more from your watch into a stream overlay. It does this by sending the data to HDS Cloud (or an IP address/port you specify). A website hosted at hds.dev can be used as a browser source in OBS to show the data. This app can save workout data to Apple Health Features: - Show your heart rate on stream with just an Apple Watch. No extra heart rate monitors required. - The app will only affect your Activity Rings if calories are enabled - Heart rate color ranges. Know where your heart rate is at a glance. - The overlay app comes with a plethora of customization options. Make your overlay look however you want. - The overlay comes with a heart beat animation that matches your real heart rate - The overlay can also play sounds to go along with the heart beat animation - Even more data for advanced users: - Motion - Every single HKQuantityTypeIdentifier available in HealthKit (so pretty much anything) Go to https://github.com/Rexios80/hds_overlay for information on how to set up the overlay.
Understanding Sleep
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This app was designed for participants in Understanding Society: The UK Household Longitudinal Study. As part of this study, participants aged 16 and over will be sent a Garmin smartwatch and asked to install and wear it, to collect data on their physical activity, sleep, and geolocation. The geolocation data will be collected directly from the respondent’s smartphone, if the phone and Garmin are within Bluetooth range. If they are not in range (suggesting that the participant has gone somewhere without their smartphone), the geolocation data will be captured by the Garmin. The purpose of this app is to retrieve all data from the Garmin as well as the geolocation data from the phone. The Garmin data will automatically be transferred to this app at regular intervals. In addition, participants will be asked to complete a brief daily survey within the app. This survey consists of 11 questions and takes less than 3 minutes to complete. The data collected by the app will not include any information about who the participant is. Understanding Society researchers will download the data collected by this app, process the data to derive indicators that do not identify you or your locations, and make the anonymous data available to researchers. The Understanding Society study is conducted by the Institute for Social and Economic Research at the University of Essex and funded by the Economic and Social Research Council.
Screenshots
Verdict
The clearest difference is price: Understanding Sleep at Free against Health Data Server's $4.99. Understanding Sleep also leads on in-app purchases (none vs 6). Health Data Server's advantage is device support (4 vs 2) and iOS requirement (14.0 vs 16.0). On update cadence and ads there is nothing between them.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
Understanding Sleep is free to download; Health Data Server costs $4.99 up front. Health Data Server sells 6 in-app purchases, starting at $2.99 per month. Understanding Sleep asks for nothing beyond the download.
Health Data Server ships an update weekly, Understanding Sleep fortnightly. The most recent releases landed on September 24, 2026 and September 10, 2026 respectively.
| Parameter | Health Data Server | Understanding Sleep |
|---|---|---|
| Price | $4.99 | Free — better |
| Rating | 3.9 (41 ratings) — better | — |
| Positive reviews | 81.8% of reviews | — |
| Number of ratings | 41 — better | — |
| Update frequency | Weekly — better | Fortnightly |
| Ads | No | No |
| In-app purchases | Yes | No — better |
| Monetization | Free with in-app purchases | — |
| Devices | iPhone, iPod, Mac, Apple Watch — better | iPhone, iPad |
| Requires iOS | 14.0 — better | 16.0 |
| Further details — not scored | ||
| Size | 27 MB | 91 MB |
| Age rating | 4+ | 4+ |
| Developer | Aaron DeLory | Avicenna Research Inc. |
In-app purchases
Health Data Server
- HDS Cloud Monthly7 Days trial$2.991 Month
- HDS Cloud Yearly$29.991 Year
- Small Tip$0.99
- Medium Tip$2.99
- Large Tip$4.99
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- Make Up the Difference$49.99
Understanding Sleep
No in-app purchases
Questions
Is Health Data Server free?
Is Understanding Sleep free?
Do Health Data Server or Understanding Sleep have ads?
Which is updated more often, Health Data Server or Understanding Sleep?
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