Heartbeats. The Apple Watch for example can show you your heartbeat in real time. Does this mean I can see my HR data on my iPhone in real time as well? I've read somewhere that apple services sync every 5 seconds, does this mean I get to see HR data once every 5 seconds?

I don't need to view the data on the iPhone, I simply need access to the data for calculations. Perhaps it could be recorded on the watch and then synced on the phone?