When selecting a pillow speaker, prioritize Bone Conduction Technology or Ultra-thin Piezoelectric Drivers (usually <10mm) to ensure comfort for side sleepers. Look for a Bluetooth 5.0 or higher chipset to guarantee stable connectivity and low power consumption. For battery-operated models, a capacity of 300mAh to 500mAh is ideal, providing 8-12 hours of continuous playtime. Additionally, ensure the device features an Auto-Power Off timer (30/60 minutes) to preserve battery life and improve user sleep hygiene.