The oscillator I want to make, should be able to change frequencies when the program is running.

Combined with the SunSPOTS, we want to use the built-in accelerometer to measure how far the users hand has traveled on the x-direction for example, and that number will be fed into the oscillator and then play the frequency of that number. So if the users movements totals a value of 560, then the program and the oscillator will play a continuous note at 560 Hz untill the user again moves the hand.