Are you talking about an app to sync your heartrate monitor with Garmin online?
Don’t know, if that is going to work.
Usually these compynies only have Windows clients (sometimes a Mac client too) but don’t care about GNU/Linux.
A quick serach has brought up this wiki page (german) on how to upgrade the firmware of specific Garmin devices.
And here a (slightly older) question with answers.
I have a situation like this by myself.
I own a TomTom naviagtion device.
There’s only a Windows client to update the device/card data…
Only way for that is either use a Windows PC just for this case (or dual-boot) or try with a Virtual system on your GNU/Linux box…