WARNING: If you use this contraption, your chat will be quickly flooded with messages, even when commandBlockOutput is false
With the 14w07a snapshot, I discovered a way to walk on water. First, you need to make a reset button to spawn your pool, and later clear the ice. The command block behind the button should turn an area to water. Make sure that the values for x1 and z1 are the lowest they can be (meaning if you look to the other corners of your area, you will be facing towards positive x or z):
/fill x1 y1 z1 x2 y2 z2 water
y1 and y2 should be the same
Next, you will need to create a 1-tick clock, and connect a command block to it, reading something similar to this (you can change the coordinates):
Put the values from the first command where x1,y1, and z1 are. In dx,dy, and dz, you will need to replace "" with the values of the first coordinates subtracted from the second coordinates. playerwalkheight is where your player will be walking, so it will be one above your y value.