All new four-wheel vehicles with a gross vehicle rating of 10,000 or less will be required to be equipped with tire pressure monitors by 2008. All passenger cars must comply by 2006. The legislation finds the cheaper "indirect" systems that use the ABS to gauge tire pressure not good enough, requiring a monitor installed on each wheel. The system will set off a dashboard warning light if any tire falls 25% below the recommended inflation pressure. Each system will cost manufacturers $48.44 to $69.89 per vehicle to install. What does this do for the huge aftermarket wheel and tire market?