Another π day special! Basically, a point is placed randomly from 0 to 1 for both x and y, and those that are less than 1 unit away from the origin are classified as being in the circle. The estimator divides those in the circle by the total number of points, and the result times 4 estimates pi.
All by me in 24 blocks! This doesn't give an exact value for pi, just an estimate that changes over time. The best part is, it uses cloud variables for the number of values and the number that made it in the circle. Because of this, it will get more precise as more people use it.