Modern Android system supports CHRE (Context Hub Runtime Environment) to run nano app on co-processor for long-running sensor-related task, to let application processor (CPU) to keep sleeping in the process. Google already takes advantage of CHRE to implement low-latency and power-saving Activity Recognition in Google Play services. This is a perfect match for Sleep as Android, and could potentially help to reduce power consumption in an order of magnitude.
At the beginning, only Google Pixel phones support CHRE (since Pixel 1). As the platform matures, more and more OEMs join. Now even my wife’s sub-$300 Xiaomi 9 SE also supports CHRE.
Please consider support sensor data collection procedure (and even mic recording, which is supported since CHRE v1.2) running on CHRE. This will also enable potentials for other new features in the future, such as auto-detection of sleeping (without much battery consumption).