(parking) BRAKE idiot light

3 days ago when I was driving under normal highway conditions, my parking brake light came on. It now comes on intermittently. The braking hasn't been affected, so I am wondering if it is a sensor or something to do with the brake fluid possibly?

Check your brake fluid level..if it is low enough to turn on the light, you have worn friction material or a leak.
Also check the park brake adjustment..have seen misadjusted PB cause this also