A vehicular rearview mirror system includes an interior rearview mirror system that has an interior reflective element, a drive circuit, a tire pressure monitoring system and a microcontroller. The drive circuit supplies a drive signal to the interior mirror reflective element, which assumes a partial reflectance level in response thereto. The tire pressure monitoring system includes a receiver for receiving signals indicative of vehicle tire pressure. The microcontroller controls at least in part the drive circuit and the tire pressure monitoring system, and may control at least one other vehicle function. The vehicular rearview mirror system may include a sound-processing system and the microcontroller may control at least in part the sound-processing system. The drive circuit may have one or more components in common with the tire pressure monitoring system, and the drive circuit and tire pressure monitoring system may be at least partially on a circuit board.