DS18B20 Temperature Driving Wemo Switch

General
2

Have you created a simple Wemo flow so that you can manually turn the switch on and off?

I would do that first.

Then how are you getting the sensor values? Direct on a Pi or something like an ESP8266?

If direct to the Pi, you can consume directly. If on an external microprocessor platform, you might want to look at using MQTT as an intermediary.