Systems and methods are disclosed for differentiating between stylus touches and non-stylus touches on a touchscreen device. A stylus emits a signal, received by the touchscreen device, and software selects a touch, the touch start event for which occurred near the time of the signal, and the size and location of which best fit filters, as being the touch made by the stylus. The software associates that touch with the stylus until the touch ends, or until the stylus emits a signal indicating that contact has ended. The signal may be mechanically generated audio, such as from the stylus contacting the screen, or electronic (audio, RF, IR), generated by the stylus upon detecting pressure or capacitive flux. The methods and systems allow software to perform palm rejection filtering, to track one stylus or multiple styluses, and to ignore touches triggered by dirt, rain, and other environmental causes.