Hear me out.....

Saying non credible af here, but in theory one could add a upwards facing shotgun shells on top of the helmet, triggered by a Camera/proximity sensor if it detects a drone/falling grande. Maybe add a gyroscope to check if the helmet is actually facing upwards before triggering. All in all unit cost could be below 250$

• 6x 12 gauge shells with bird shot
• Raspberry pi type controller
• USB cam
• Laser distance sensor
• gyroscope
• servo trigger