"When you are a hammer", the proverb goes, "everything looks like a nail".
To my knowledge current apnea testing involves a multitude of sensors that record the position of various parts of the body but do not evaluate the position and motions of the jaw and the number of apnea events indicates either a go/no-go decision about CPAP.
However, the location of the jaw can in some cases be manipulated by a physical appliance resulting in a relatively simple, passive solution.
In fact, armed with sufficient data it may be possible to identify currently unidentified jaw and dental problems that might be creating or contributing significantly to the apnea.
In addition the collected data may lead to other insights such as a patient shown to be grinding their teeth, resting their jaw on their hand during sleep, etc.
I would imagine that all that would be involved is a sensor on the skull (already present) and one (or better yet, three, for each axis) on the jaw.
Note: At the heart of this is my suspicion that dental and jaw issues account for a significant part of apnea, confirmed by the efficacy of the new appliance.