Frontier X

Name: Frontier X
Author: Fourth Frontier Technologies Private Limited

12.4.0.3

Play Protect

Fourth Frontier Technologies Private Limited

10K+ installs

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Companion App of Frontier X/X2/X3 for runners, cyclists and endurance athletes

Frontier X app: ECG and heart data from a chest strap

By Mei-Lin Chua

Contributing editor, apps and storefronts

Continuous ECG recording during exercise, rest and sleep
Heart rate variability, breathing rate and stress readings
Strain and training load figures for each workout
Rhythm data shown alongside heart rate and calories
Connects to the Frontier X, X2 and X3 chest strap

What the Frontier X app is for

Frontier X is a companion app for the Frontier X, X2 and X3 chest strap, a worn heart monitor that records an ECG signal. The app pairs with the strap and shows the data it collects. The listing names runners, cyclists and endurance athletes as the intended users.

The strap is worn on the chest, so the recording continues through training, rest and sleep. The developer says the strap gives real-time feedback during activity, and the app is where that data is read back and reviewed afterwards.

ECG recording and heart rhythm data

The app's main function is the ECG record. The listing describes continuous 24/7 recording, so the same trace covers a run, a rest day and a night's sleep. Rhythm readings from that trace are listed as a separate item.

Heart rate is shown from the same strap. The listing lists it next to the ECG data, so a person can compare rhythm and rate for one session.

Training load, strain and calories

For training, the app reports strain and training load. Strain is a measure of how hard a session was, and training load adds up effort across sessions. The listing also includes calorie totals for each activity.

These figures are meant for planning and tracking a training block. The listing does not say how the scores are calculated, so the app's own explanations are the place to check what each number means.

Heart rate variability, breathing and stress

Heart rate variability (HRV) is the variation in time between heartbeats. The app reports HRV along with breathing rate and a stress reading. The listing presents these as recovery and wellbeing measures, separate from workout data.

A reader who wants to follow recovery over several days would look at these readings next to training load. The listing gives no further detail on how they are shown.

What's new

Oct 6, 2026

Enhanced Bluetooth security for Frontier X2 devices with Secure BLE Pairing/Bonding.
Bug fixes and performance improvements

About this APK

The build we hold is Frontier X 12.3.0.2 (APKS split bundle) for Android 8.0 and up.

Version: 12.3.0.2; 328
Requires Android: 8.0+
Target Android: 15

Package ID: com.fourthfrontier.biostrip
Format: APKS split bundle
Malware scan: Google Play Protect
Permissions: 44 declared · 3 sensitive; Approximate location
Precise location
Read phone status and identity
Signed by: CN=Android, O=Google Inc.
Certificate SHA-256: cdb437f8301a5d0a46cab6cae4347e6100f602ea59be27edb933c3ac7d67e737