SleepLog - Adding heart rate

Has anyone already tried adding heart rate to SleepLog?

A single max heart rate like sleepHR that says to only consider sleep if heart rate is below that value (in my case ~58-60bpm).

Based on motion alone I get a lot of false positives during the day based on motion, if I'm at my desk for 30 min, or at the dentist, etc. (And then there's often a base level of ~50-80 reported even if I'm not wearing the watch...)

I've been trying the heart rate plan and I still get false positives if the heart rate gives a 0 for whatever reason, so I've also considered holding onto the most recent nonzero for a while.

I also considered trying to store min/max heart rate and basing sleep on the lowest 15th percentile. But for myself just setting a bpm is easy enough.