ShiftIn and ShiftOut are not currently supported by StandardFirmata. There is a proposal to add that functionality but it may not be for a few more months.

There is another way to use Breakout in which you write your own firmware for the Arduino rather than using StandardFirmata. This way you can send any type of data between the Arduino board and your browser. At this point I don’t have a tutorial on writing custom firmware for Breakout, but there are a couple of examples. Refer to Breakout/custom_examples. I hope to post a tutorial soon though.