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Auxiliary Heart Rate


A simple data field that connects to ANT+ heart rate monitors, displays heart rate (in bpm), and records it into the FIT file.</p><p>This was developed so that I could use the built-in optical heart rate monitor on my Forerunner 235 and an external ANT+ chest strap at the same time, logging values from both for comparison.</p><p>Note that you should not have the external ANT+ heart rate monitor paired to the watch in the usual fashion, the data field will make its own connection.

What’s New

Version 1.1 added the ability to set the ANT+ ID of the external heart rate monitor you wish to connect to. Set it to zero (the default) to search for any HRM (it will select the strongest signal, probably, once connected it won't switch to another HRM).


Companion Hardware

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Additional Information


This app requires access to:

  • Send/receive data via ANT radio to/from third-party sensors
  • Record additional information into activity files
  • D2™ Bravo D2™ Bravo
  • D2™ Bravo Titanium D2™ Bravo Titanium
  • D2™ Charlie D2™ Charlie
  • D2™ Delta D2™ Delta
  • D2™ Delta PX D2™ Delta PX
  • D2™ Delta S D2™ Delta S
  • Descent™ Mk1 Descent™ Mk1
  • Edge® 1000 Edge® 1000
  • Edge® 520 Edge® 520
  • Edge® 520 Plus Edge® 520 Plus
  • Edge® 820 Edge® 820
  • Edge® Explore 1000 Edge® Explore 1000
  • Edge® Explore 820 Edge® Explore 820
  • ForeAthlete® 230J ForeAthlete® 230J
  • ForeAthlete® 235J ForeAthlete® 235J
  • ForeAthlete® 630J ForeAthlete® 630J
  • ForeAthlete® 735XTJ ForeAthlete® 735XTJ
  • ForeAthlete® 920XTJ ForeAthlete® 920XTJ
  • Forerunner® 230 Forerunner® 230
  • Forerunner® 235 Forerunner® 235
  • Forerunner® 630 Forerunner® 630
  • Forerunner® 645 Forerunner® 645
  • Forerunner® 645 Music Forerunner® 645 Music
  • Forerunner® 735XT Forerunner® 735XT
  • Forerunner® 920XT Forerunner® 920XT
  • Forerunner® 935 Forerunner® 935
  • fēnix® 3 fēnix® 3, quatix® 3, tactix® Bravo
  • fēnix® 3 HR fēnix® 3 HR
  • fēnix® 5 fēnix® 5, quatix® 5
  • fēnix® 5 Plus fēnix® 5 Plus
  • fēnix® 5S fēnix® 5S
  • fēnix® 5S Plus fēnix® 5S Plus
  • fēnix® 5X fēnix® 5X, tactix® Charlie
  • fēnix® 5X Plus fēnix® 5X Plus
  • fēnix® Chronos fēnix® Chronos
  • vívoactive® vívoactive®
  • vívoactive® HR vívoactive® HR
Average Rating: (26 Ratings)

January 15, 2022

Works well. It does seem that the added data recorded to the watch causes some synch issues. I have an FR235 and runs over 20 miles only synch to my iPhone after about 25 tries. I assume I could use a computer to DL the activity without issue.

Chris Jones
October 24, 2021

The app is great. Is there a reason it's compatible with FR235 but not the FR245. The wider Garmin ECOsystem seems far from straightforward. Thanks Chris Messages to developers seem to fail (Garmin connect message server fails)

December 30, 2020

Simply perfect. Thank you

April 12, 2020

Hi, thanks a lot for this simple and great app! It works perfectly on my FR235, and I use it to compare the built-in heart rate sensor with the external strap. Would it also be useful to make it compatible with the Vivoactive 4S? Many watches are supported, but unfortunately this one is not in the list. I would like to also compare the built-in heart rate sensor of that watch with my external strap. Thanks in advance!

Kristen Wangerin
February 14, 2020

Cool! I look forward to playing with this data more. For others out there, I got this to work most easily (on my Mac) using fitdump: 1) Download fitdump and GarminFIT packages. 2) Extract both. 3) Put the Fit file you want to read as well as the Garmin folder (which will contain the file in the same directory as the fitdump execuable. This way fitdump will find Garmin::FIT. 4) Run: ./fitdump

Chris Dunhill
April 19, 2019

Can't get this to work. Fenix 5+, latest firmware updates. Unpaired Polar HRM, added the ANT+ code (AND tried with 0) but data field just says "searching". Am I missing something?

Developer Reply
December 19, 2019, IMGrant

I don't think Polar HRMs are ANT+?

Bruce Tiller
January 10, 2019

Great app - it allowed me to directly compare wrist based measurement on new watch (Forerunner 235) to chest strap i have worn for last couple of years. They compared very well in my case and it gives me more confidence in the watch going forward. Thanks for a very simple and useful tool!