Comparison

Frontier X vs Calibrex App

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

Frontier X

Track your heart health and exercise performance with a smart chest strap monitor. Gain detailed insights into heart rate, rhythms, and training load. Receive personalized feedback and alerts to optimize your workouts and understand your body better.

Highlights
  • Heart Health Monitoring
  • Real-time Heart Rate & HRV
  • Breathing Rate & Strain Tracking
  • Activity Recording (24hrs)
  • Personalized Vibration Alerts
  • AI-enabled Training Insights
  • Metabolic Profile Analytics (Premium)
Features
Read full description

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.

About

Calibrex App

This wearable device precisely tracks your weightlifting reps, rest, and movements. It provides personalized insights into your training, offering live audio coaching and tailored workouts to help you achieve your strength, speed, or endurance goals.

Highlights
  • Precise rep, rest, and movement tracking
  • Live audio coaching tailored to goals
  • Personalized insights into training performance
  • Advanced tracking and tailored workouts
  • Set Score, Difficulty Score, Speed Score, Tempo Score
  • Discover training trends and program balance
Features
Read full description

Meet Calibrex — the wearable built for lifting. Calibrex is a tiny magnetic wearable that captures every rep, rest, and movement with unmatched precision — giving you deep, personalized insight into your training, and live audio coaching. Whether you're chasing strength, speed, or endurance, Calibrex adapts to your goals and pushes you further with intelligent feedback, advanced tracking, and tailored workouts that grow with you. Get coached through every set with live audio feedback — tailored to your goals, training style, and performance history. Set Score – How well you executed each rep and how intensely you pushed. Difficulty Score – How close you came to muscle failure. Speed Score – How closely your rep speed matched your target training zone. Tempo Score – How much time your muscles spent under tension. Discover powerful trends across your training — like increasing bench press volume, longer rest times, or missed muscle groups. Get a clearer picture of how balanced your program is across your entire body. 25M Reps & Counting. 1500 + professional weightlifters, coaches, university programs, and fitness enthusiasts across more than 15 countries.

Screenshots

Frontier X4 screens
Calibrex App4 screens

Verdict

The call

The clearest difference is rating: Frontier X at 4.6 against Calibrex App's 3.5. Frontier X also leads on review sentiment (82% vs 50%) and ratings volume (318 vs 11). Calibrex App's advantage is in-app purchases (none vs 2). On price, update cadence, ads and device support 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

CostPrice · In-app purchases · Ads · Monetization

Both are free to download. Frontier X sells 2 in-app purchases, starting at $14.99 per month. Calibrex App asks for nothing beyond the download.

ReceptionRating · Positive reviews · Number of ratings

Frontier X holds the better App Store score, 4.6 against 3.5. That said, the two scores are not equally well evidenced: Frontier X has 318 ratings behind it against 11, so its average is the more settled of the two. Written reviews point the same way: 82% of Frontier X's written reviews are positive against 50% of Calibrex App's.

UpkeepUpdate frequency

Frontier X ships an update every 3 weeks, Calibrex App fortnightly. The most recent releases landed on October 25, 2026 and October 24, 2026 respectively.

Scorecard5 real differences · 5 level
Frontier X versus Calibrex App: the parameters behind the verdict, then further details
ParameterFrontier XCalibrex App
PriceFreeFree
Rating4.6 (318 ratings) — better3.5 (11 ratings)
Positive reviews81.8% of reviews — better50.0% of reviews
Number of ratings318 — better11
Update frequencyEvery 3 weeksFortnightly — better
AdsNoNo
In-app purchasesYesNo — better
MonetizationFree with in-app purchasesFree — better
DevicesiPhone, Apple WatchiPhone, iPad, iPod — better
Requires iOS16.015.1 — better
Further details — not scored
Size569 MB150 MB
Age rating4+12+
DeveloperFourthfrontierCalibrexInc

Customer experience

Frontier X

All ratings318 ratings
Positive90.9%
Neutral1.3%
Negative7.9%
Written reviews137 reviews
Positive81.8%
Neutral1.5%
Negative16.8%

Calibrex App

All ratings11 ratings
Positive54.5%
Neutral0.0%
Negative45.5%
Written reviews8 reviews
Positive50.0%
Neutral0.0%
Negative50.0%

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
Show 1 more
  • Improve data visualization and analysis tools

Calibrex App

Not enough reviews yet to summarise bugs or requests.

In-app purchases

2 purchases

Frontier X

Subscriptions2
  • Monthly7 Days trial$14.991 Month
  • Yearly7 Days trial$119.991 Year
None

Calibrex App

No in-app purchases

Questions

Is Frontier X free?
Frontier X is free to download, with in-app purchases available.
Is Calibrex App free?
Calibrex App is free to download, with no in-app purchases.
Which has better reviews, Frontier X or Calibrex App?
Frontier X is rated higher. Frontier X averages 4.6 out of 5 from 318 ratings, while Calibrex App averages 3.5 from 11 ratings.
Do Frontier X or Calibrex App have ads?
Neither Frontier X nor Calibrex App shows ads.
Which is updated more often, Frontier X or Calibrex App?
Frontier X ships an update every 3 weeks, and Calibrex App fortnightly. Most recently, Frontier X was updated on October 25, 2026 and Calibrex App on October 24, 2026.

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