Frontier X vs Nix Solo
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
Frontier X
Track your heart health and exercise performance with a smart chest strap wearable. Get detailed insights into heart rate, HRV, strain, and more, with personalized training feedback and alerts. Integrates with other devices and offers advanced analytics through a premium subscription.
- Heart health and performance tracking
- Real-time heart rate and HRV monitoring
- Personalized vibration alerts
- Activity recording up to 24 hours
- Integration with Bluetooth wearables
- AI-enabled training insights
- Metabolic Profile Analytics (Premium)
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With your Frontier X/X2/X3, track your activity including exercise, rest or sleep to get detailed insights on heart health and exercise performance. This companion app allows you to connect with Frontier X2/X3 - a revolutionary chest strap wearable smart heart monitor and view your recorded data. Trusted by world-class athletes across the globe, the Frontier X2/X3 is a chest-worn Smart Heart Monitor that provides in-depth real-time feedback on your heart health. It can monitor your: - Heart Health - Heart Rate - Heart Rate Variability (HRV) - Breathing Rate - Strain - Rhythms - Training Load - Calories - Stress, and a lot more. • Accurately record your activity like exercise, running, cycling, resting, sleeping, meditation, etc for up to 24hrs with comprehensive heart health insights. • Spot changes in your heart health with Rhythm and Strain. • Train in the right zone without distractions with real-time, personalized, and discreet vibration alerts. • Add health event tags to help you understand how lifestyle choices and behavior affect your health. • Seamlessly integrate with Bluetooth-enabled wearables and third-party devices such as GPS sports watches, bike computers, and more. • AI-enabled algorithms - Receive post-activity training insights, recommendations, and weekly goals. • Frontier X integrates with HealthKit to export your Frontier X activities into the Health app and to read heart rate and biometric data. • IP67 Waterproof up to 1.5 M • Battery: 14+ days of typical use Now get deeper insights and data with Frontier Premium Subscription*: Metabolic Profile Analytics: Track training intensity and the impact of lifestyle changes on metabolic health with key metrics like VO₂ Max, VO₂ Zones, Oxygen Uptake, and Ventilatory Thresholds (VTs). VO₂ Max: Get the most accurate real-time VO₂ Max data. While other wearables estimate using motion and heart rate, our advanced algorithms provides precise VO₂ Max readings outside of a lab, tracking cardiovascular efficiency and endurance potential. Readiness Score: Determine if your body is ready for peak performance or needs recovery. Advanced algorithms use heart rate, heart rate variability (HRV) to guide your daily activities and training. Sleep Stage Analysis: Get a comprehensive understanding of your sleep quality (Webapp). With Frontier's Premium subscription and Metabolic Profile Analysis, tracking your VO₂ max becomes simpler and more precise. *A Paid Frontier Premium subscription is required to access the full feature set . The Premium feature subscription comes with a complimentary 7 days free trial, and continue at a minimal monthly cost starting from USD 14.99, or opt for an annual plan for substantial savings. Please note that prices may fluctuate based on your geographical location, currency, and current exchange rates The Terms of use are available in the app and our website: https://in.fourthfrontier.com/pages/terms-of-use About Fourth Frontier Fourth Frontier is an innovative health-tech company focused on revolutionizing heart health monitoring with its cutting-edge wearable technology. We are the World’s First Smart Heart Monitor. With over 5 billion heartbeats recorded from 120,000+ users across 50+ countries, we are empowering users to understand and manage their heart health in real-time. These features make the Frontier App a comprehensive tool for heart health management and fitness improvement. Download the app today and access the most accurate heart health data available. Apps available for iPhone and Apple Watch.
Nix Solo
Monitor personal fluid and electrolyte losses in real-time during workouts. This app provides insights into sweat composition and hydration needs based on individual biology, using data from a companion biosensor.
- Real-time fluid and electrolyte loss monitoring
- Personalized sweat composition insights
- Correlates sweat data with environmental factors (Nix Index)
- Post-workout Sweat Intelligence reports
- Integration with Apple Watch and Garmin devices
- Workout type and hydration input
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To train at your peak, you can’t just train hard. You need to train in a way that’s informed by your personal biology. The Nix Solo app allows users to monitor their own personal fluid and electrolyte losses in real time during a workout using the Nix Hydration Biosensor. This companion app provides valuable insight into their unique sweat composition and individual hydration needs based on their personal biology. At Nix, we built the first biosensor to analyze sweat and provide endurance athletes with personal hydration data – scientifically validated, and delivered in real time. Once paired with the Nix Hydration Biosensor, you are on your way to understanding your hydration needs with Nix Solo, our individual monitoring app. We’re the first hydration biosensor of its kind — the only pod, patch, and free app combination to: - Evaluate the electrochemical biomarkers in your sweat - Send real-time updates to your phone, Apple Watch, Garmin Watch, or Garmin Bike Computer - Correlate your sweat data and your training environment with the Nix Index – a composite index of six environmental factors: temperature, humidity, dew point, altitude, wind speed, and solar load - Provide post workout Sweat Intelligence via insights on your Sweat Profile including fluid loss rate, electrolyte loss rate and sweat composition metrics Before your workout, tell the Nix Solo app what type of workout you’re doing and what you’ll be hydrating with. You can also consult the Nix Index to see how your environment impacts your hydration needs. Once you start sweating, our single-use patch begins measuring and analyzing your fluid and electrolyte losses minute by minute- metrics that represent your unique “sweat composition.” This data is instantly streamed to our app, and can also be shared with devices like your Apple Watch, Garmin Watch, and Garmin bike computer. The result is knowing when, what, and how much to drink in real time to enhance both safety and performance.
Screenshots
Verdict
The clearest difference is review sentiment: Frontier X at 82% against Nix Solo's 14%. Frontier X also leads on ratings volume (318 vs 68). Nix Solo's advantage is in-app purchases (none vs 2) and rating (4.8 vs 4.6). On price, update cadence, ads and iOS requirement 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
Both are free to download. Frontier X sells 2 in-app purchases, starting at $14.99 per month. Nix Solo asks for nothing beyond the download.
Nix Solo holds the better App Store score, 4.8 against 4.6. Both are backed by a comparable volume of ratings — 318 and 68 respectively. Written reviews complicate that: 82% of Frontier X's written reviews are positive against 14% of Nix Solo's, so the app with the better star average is not the one people write more warmly about.
Frontier X ships an update every 2 weeks, Nix Solo every 10 days. Both last shipped on November 3, 2026.
| Parameter | Frontier X | Nix Solo |
|---|---|---|
| Price | Free | Free |
| Rating | 4.6 (318 ratings) | 4.8 (68 ratings) — better |
| Positive reviews | 81.8% of reviews — better | 14.3% of reviews |
| Number of ratings | 318 — better | 68 |
| Update frequency | Every 2 weeks | Every 10 days — better |
| Ads | No | No |
| In-app purchases | Yes | No — better |
| Monetization | Freemium | Free — better |
| Devices | iPhone, Apple Watch | iPhone, iPad, iPod, Apple Watch — better |
| Requires iOS | 16.0 | 15.1 — better |
| Further details — not scored | ||
| Size | 569 MB | 65 MB |
| Age rating | 4+ | 4+ |
| Developer | Fourth Frontier Technologies Private Limited | Nix, Inc. |
Customer experience
Frontier X
Nix Solo
Bugs and requests
Frontier X
Reported bugs
4 issues- ECG stopped working
- Inaccurate breathing rate and other metrics
- Inability to edit activity details for indoor workouts
- Syncing issues with Garmin devices after firmware updates
Requested features
6 requests- Add interval markers
- Improve integration with Apple Fitness/Fitness+
- Add support for ANT+
- Improve compatibility with other fitness apps and devices
- Add more customization options for workouts
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- Improve data visualization and analysis tools
Nix Solo
Not enough reviews yet to summarise bugs or requests.
In-app purchases
Frontier X
- Monthly7 Days trial$14.991 Month
- Yearly7 Days trial$119.991 Year
Nix Solo
No in-app purchases








