The SAWATCH-3 (サウォッチ3), the third-generation sauna-specific wearable device from Tokyo-based 100plus, is now available for pre-order. While sauna has become an established health habit in Japan, the company developed the SAWATCH series to provide objective, data-driven insights that help users safely and more deeply enjoy each session — rather than relying solely on intuition.
After a major measurement performance update in the second-generation SHOWDOWN-1, SAWATCH-3 has been redesigned from the ground up, with improvements to durability, stability, and sauna-specific measurement capabilities. This generation also extends tracking beyond the sauna itself, covering daily activity, stress levels, and sleep, helping users understand how sauna affects their overall wellbeing.
Real-Time Autonomic Nervous System Monitoring
New Features: "Strain" and "Slope"
Strain displays the state of the autonomic nervous system in real time during the sauna room, cold bath, and rest phases. It lets users check whether they are experiencing excessive load in the sauna or cold bath, and whether they are properly relaxing during the rest period.
Slope shows the rate of change in heart rate in real time. By monitoring the speed and intensity of rising heart rate, users can proactively manage their exposure before it becomes excessive.
Recommended Usage Tips
In the sauna room:
During the first half, monitor Slope to adjust the rate of heart rate increase — it differs between the 1st, 2nd, and 3rd sets, so move to a lower or higher bench accordingly. In the second half, switch to Strain, which is shown on a 7-level scale. Consider leaving when Strain reaches 5 or 6; reaching 7 means the load has already become excessive. Combining breath control with these indicators is a good approach.
In the cold bath:
Watch Slope. Heart rate drops sharply when entering the cold water, then gradually stabilizes. When Slope approaches 0, that's the right time to get out.
During rest:
This phase is considered the most important. Focus on Strain — it takes a short time to begin measuring (displaying 0 in the meantime), then shows a number from 1 to 7. If the first reading shows 1 or 2, that indicates proper relaxation. A Strain of 1 is perfect.
By adjusting load and timing across the sauna, cold bath, and rest phases, users can fine-tune the entire session in real time.
Advanced Features: "Timeless" and "Meditation Sauna Mode"
Timeless is a feature that removes the time display during sauna mode. It can be toggled in the "Sa no Kuni" companion app settings. Without time visible on screen, only heart rate and autonomic nervous system data are shown, making it easier to focus on personal sensation rather than the clock.
Meditation Sauna Mode ("Meisou" mode) takes this further — the screen goes completely dark while measurement continues in the background. Designed for advanced users, it enables full immersion by removing all visual distractions.
The recommended progression is to start with standard sauna mode to get a feel for the data, advance to Timeless to reinforce that awareness, and finally use Meditation Sauna Mode to verify your intuition.
Seven Key Improvements
1. More Flexible Notification Settings
The SAWATCH-3 allows independent notification settings — by heart rate and time (or both simultaneously) — for each phase: sauna room, cold bath, and rest. For example, a user can set a 130 bpm alert for a regular sauna, switch to 120 bpm or 10 minutes for a low-temperature sauna, 30 seconds for the cold bath, and 5 minutes for rest. This level of per-phase customization responds to one of the most frequently requested features from users.
2. Beyond the Sauna: Daily Activity, Stress, Sleep, and Recovery
SAWATCH-3 is not limited to sauna sessions. It records activity levels, stress, sleep, and recovery, allowing users to look back on how sauna affects their daily condition — on both sauna and non-sauna days. The device is designed to be worn continuously as an everyday watch.
3. Everyday Functions Including Timer and Alarm
With expanded basic functions such as timer and alarm, the SAWATCH-3 is designed to transition from a device worn only during sauna to one that monitors daily condition throughout the day.
4. Customizable Watch Faces
The home screen watch face can be freely changed. Limited edition watch faces tied to events and campaigns are also planned for future release, extending the appeal of the device into everyday life.
5. Advanced Sensor for Higher Vital Measurement Accuracy
A new sensor improves the accuracy of heart rate and other vital data — not only during sauna sessions but also during regular daily use and sleep. This enables a more precise picture of how sauna influences physical condition.
6. High-Resolution AMOLED Display
The SAWATCH-3 features a high-resolution AMOLED display for clear readability in the bright sauna room environment and in outdoor daylight conditions. In darker sauna settings, brightness can be reduced to avoid unnecessary screen glare.
7. Fully Original Hardware Design with Enhanced Heat Resistance and 1-Year Warranty
Drawing on experience from previous SAWATCH models, the SAWATCH-3 uses a fully original hardware design built specifically for the high-heat, high-humidity sauna environment. Destructive testing at temperatures beyond the rated operating range was conducted during development to verify safety. The warranty period has also been extended to one year.
Two Color Options
The SAWATCH-3 is available in two colors: Matte Black and Champagne Gold. Both are designed to suit everyday wear for all genders, in addition to sauna use.
Integration with the "Sa no Kuni" Companion App
SAWATCH-3 pairs with the "Sa no Kuni" (サの国) companion app (detailed measurement data requires app connection). Heart rate data synced through the app is displayed on the sauna log ("Sa-roku") screen, including a heart rate graph and a "Totonou Score" that lets users review their session objectively.
The Sa no Kuni app also includes a sauna facility search function, achievement badges, session summary features, and a sleep log display — all aimed at sauna enthusiasts.
Pricing and Availability
- Price: ¥24,800 (tax included); shipping ¥730 (nationwide flat rate)
- Estimated shipping: Mid-to-late May 2026 (first batch); mid-June 2026 (second batch)
- Pre-orders: Available at the 100plus web shop: https://100plus.stores.jp
Product Specifications
| Item | Details |
|---|---|
| Product name | SAWATCH-3 (サウォッチ3) |
| Body size | 48.5 mm × 25.7 mm × 11.5 mm |
| Strap width | Approx. 16 mm |
| Strap fit | 166 mm–232 mm wrist circumference |
| Weight | Approx. 28 g |
| Colors | Black, Champagne Gold |
| Case material | Fiber-reinforced polymer |
| Strap material | Silicone / stainless steel (clasp) |
| Display glass | Mineral glass |
| Display | 1.72-inch / 212 × 520 px (AMOLED) |
| Charging | Dedicated magnetic cradle (USB-A) |
| Charging time | Approx. 2 hours |
| Battery life | Approx. 5–7 days (varies by usage) |
| Operating temperature (internal design) | -10°C to 100°C |
| Water resistance | IP68 / 5ATM |
| Battery | High-temperature-rated battery |
| Technical certification | Pending (Japan) |
Recommended sauna use conditions: Wear the device on your wrist in a sauna room where the displayed temperature is 100°C or below. Limit each session to approximately 20 minutes. Do not leave the device unattended inside the sauna, as internal temperature may rise significantly when not worn. Stop use immediately if abnormal heat, unusual smell, or deformation is observed.
Warranty: 12 months from the date SAWATCH-3 is first connected to the Sa no Kuni app.
