[RELEASE] Official Monoprice 4 in 1 Motion Sensor with Temperature, Humidity, Light, Battery and Tamper Notifications Device Handler

here’s a good topic to links with discussions on new app vs classic app. FAQ: New SmartThings App

You can use both apps at the same time. There is also a custom automation creator in the new app that allows you to control devices on many types of conditions (including humidity). for anything too complex, you may have to find a dedicated app like RBoy linked to above or use Webcore.