$11.69 (reg. $12.99) with coupon on Amazon
Too much humidity in the attic can be a problem that might end up costing you tens of thousands of dollars if you are unlucky. Humidity levels can widely vary by day and time of year, and this is a great, low-cost way to monitor remotely without having to go up there. I set this up in my attic, and can look up humidity levels with an app on my phone (I had no problem getting Bluetooth connectivity)!
