Do not put plastic wrap over the top of the sous vide device. Wrap it around the step where it comes out of the water.
There is a company that makes "sous vide balls" that will control the condensation. I've also heard of people using ping pong balls. Here is a link to one on Amazon:
http://www.amazon.com/Sous-Vide-Wate.../dp/B013NYKAU4
My Inova says to not submerge the control unit when cleaning but I do get condensation on the unit when cooking. If it were to fail for that reason, I'd demand a replacement and report them if they didn't come through (selling a defective product will get you kicked off of Amazon in a hurry).