Here is a tiny gadget that lets you keep a close eye on humidity and temperature readings in your home. The ViseeO QUBS weighs only 39g, measuring 46mm x 46mm x 18.5mm. You can track multiple devices at the same time without a hub.
The device has a large memory to log years of data for analysis. You can set a range to get alerted. This smart humidity and temperature sensor is available for under $50 at this time.