Used this for a little while this summer, in a nutshell if your running one of the simple 1D or 2D alky systems based on either boost or MAF, etc.., this allows other inputs to modify the 0-5V signal sent to the spray. My intention with this was to allow a signal to be based off of MAF, IAT, and boost. I guess in other words this would be a piggyback controller to any of the 0-5 voltage based controllers out there. Also can be used to trigger or run almost any device outside of a alky controller also. I used it as a datalogger this summer also, you can sample and record also using the PC.
Worth reading if interested,
http://www.coolingmist.com/detailmain.aspx?pid=1099
comes with a good 3/4 inch user manual

, additional IAT sensor, PC connections, and a couple nikel plated quick connect T nozzles 250ml/350ml.
$100.00 shipped