Standing at a dimly lit garage one rainy evening, I reached for my keys with a sinking feeling. My friend, recently recovered from a DUI, had installed a car interlock device, a personal sobriety monitor that controlled his vehicle’s ignition. It slid into the ignition like a well-fitted key, but it was much more than a mere gadget. I watched as he blew into the device, its screen flashing ominously in the shadows. That moment left me curious: how did this technology really work, and what implications did it have for not just individual drivers but society at large?