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?

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?