Aquaero is not capable of humidty sensing (despite it being mentioned in the manual as an option under digital sensors, the humidity sensors even use the same bus as the aquabus but something isn't compatible and it's not capable of computing dew point anyway) after a few PM's with shoggy we worked out it would need to be a special add in board to get it to work with aquaero. Only option is to set a nominal figure below ambient for the controller to hold, risky though as dew point fluctuates so much, would still need insulation for safety. Its perfect if you don;t mind going under dew point in combo with an RSP-xxxx PSU.
So arduino or the USBee thing with a temp, humidity sensor that can do the dew point calculation and ideally has software monitoring and control with that driver board that you are making master chicken would be great. Foxrena has done most of the hard work with arduino control already so if you did the driver and he did the control and you sold it as a package we'd finally have an easy solution like the old arqtik setup.
for $45 it's hard to compete with that tiny controller I have, but no software control or monitoring, and no dew point control. I do my monitoring with XSPC LCD's and aquasuite through sensors on cold, hot, water etc.