I would look at one of the bathroom fan humidity apps. I use Smart Humidity Fan, but there is a couple others.
Also, there was a good tip from csteele about using tape to narrow the sensor beam. I use either a short stub of PVC plumbing pipe, or for a more clean look a plastic "EMT conduit bushing" that is a very thin and nearly perfect size that is intended to keep wires from rubbing on metal conduit. I just hot glue them in place. They come in various sizes, but be careful about electrical stuff not being actual (measured) diameter. These 1/2 are what I used for an Iris V3.
www.amazon.com/Arlington-EMT50-100-Insulating-Electrical-100-Pack/dp/B00422M1R2
