The Emfit QS will be directly underneath the blue circle (where the manual is).
I will be in a sleeping position so that my heart is somewhere inside the red circle (where the pillow & manual is).
I did use with a partner, a number of years ago, and that version of it seemed to detect my sleep as reasonably well as one could hope based on heartbeat vs. EEG.
The problem I experience now is that if I sleep until 7 am and then go to the other side of the bed for 30 minutes (mimicking having a partner sleeping there 30 minutes after I wake up), then it think I’m sleeping or still in the bed in that period)