/\ Don't jump the gun here... An intermittent high pitched squeaking that goes away under any steering movement or even a touch to the brake pedal more often than not is the brake pad wear sensor.
Check your pads, and I'm willing to bet you'll find they are quite worn.
If they are not, then it's still a possibility that it could be the pads, and that they're vibrating and squealing. When you've got the wheel off to inspect the pads, take the caliper off, grease the slides, and grease where the pads ride on the caliper. Spray some brake quiet on the backing of the pads, and if the pads are worn to the sensors, bend them back ever so slightly and order pads as soon as you can.