Here is another use for the detachable headrest in cars
The headrest is an important part of the restraint system in a car, and everyone who uses a backless booster or a seatbelt should have one. Headrests are crucial for preventing neck hyperextension in a collision because it might mean the difference between a spinal cord injury and an ordinary whiplash. So, the following second purpose may be a great hidden trick.
Potentially, you could use the removable headrest to break the windows of your vehicle in case of an accident. But you should keep in mind that not every vehicle has removable headrests and it may not be a part of the primary design of all vehicles. And although it is better if that day never comes, now you know how to be prepared for it.