I accidentally downloaded an app called HR Broadcast and found a way to transmit my heart rate via Bluetooth.
It seems like it would be useful when you forget your heart rate monitor or don't have one with you.
As a result of using it, the Apple Watch battery drains faster than I expected,
(you need to run the app on the watch for continuous transmission to the speedometer)
My heart rate was displayed well on the speedometer except for a couple of brief interruptions in between. It might be a bit much for long distances, but
it seems like a great option for short-distance use...
