There was a HN post a few months ago, [sadly I can't find it] which correlated healthy sleep with faster card answering times in Anki.

I haven't used Supermemo, but believe it has fairly strong sleep tracking capabilities.

I've dabbled about doing the same in AnkiDroid. We could pull data from Android Health, and do something interesting with it, but we've got hundreds of other things to do, Google will probably pull our app from the Play Store if we request health data, and it at the moment it's a little out-of-scope and would be better for an addon using our API