The problem with schemes like this, is that they show premeditated intent to destroy evidence. I hear that courts don't like that. Maybe there wouldn't be evidence that specifically unplugging the headphones is what caused the drive to self destruct. But a good forensic security analyst should be able to show that the system was intentionally destroyed.
If you can come up with a plan for plausible deniability when it comes to, say, permanently deleting the keys for an encrypted drive, then that's worth way more than the deadman's switch is on its own.
If you can come up with a plan for plausible deniability when it comes to, say, permanently deleting the keys for an encrypted drive, then that's worth way more than the deadman's switch is on its own.