Millions of sub-prime borrowers have made car purchases contingent upon having an unusual option: a little box mounted underneath the dashboard that forces them to make their payments on time. A light on the plastic box flashes when a payment is due. If the payment isn't made and the resulting code punched in to reset the box, the vehicle won't start.. This year car and truck repos are predicted to hit the highest level in at least a decade, according to USAToday.

As more dealers look for ways to protect themselves, Sekurus, maker of these "On Time" devices, has a revenue goal of $20 million this year. Car dealers say most customers aren't thrilled to punch in a code with every payment but grow accustomed to the device. "We've used it as a tool to keep the repo rates down," says Jeff Hamilton, partner in Hamilton Classic Cars in Chester, Va. "We don't have to go after them as much." Most of his customers are required to make payments twice a month, and often wait until the last day, "when it starts beeping at them."