I use the sensorpush from Amazon. They are not pre calibrated but you calibrate them easily through the app. I replaced most of my hygrometers with them and haven't had any issues at all. I did have issues with the wireless gateway they sell. They sent me 3 different ones and none worked with a note 4, galaxy s8+, or a nexus 6p.
I did find that all of them were nearly spot on on the temp, and a +/- 1-3% on rh