I use an RTL 515 with a Garmin Edge 1000. The edge 1000 alert sound isn't very loud (it is louder in later 1030 etc).
I have started using the Varia Radar app on my iPhone so that the alert tones can be heard clearly through my Aftershokz bone conduction headphones, but over a 4 to 5 hour ride, the battery drain on the phone is excessive, using up to 70%!
If the Varia Radar App could be set to give Audible Alerts ONLY then I assume the battery drain on the phone would be reduced.
Do any other headphone users feel this would be useful?