You could have downloaded ShadowBook 1.1 for Mac from our application library for free. The application is included in System Tools. This free Mac app is a product of Medallia.
From the developer:
The application will trigger if the left sensor value is below the threshold, and the right sensor is above. Due to what appears to be a hardware bug the right sensor cannot be used a trigger. This program can send a notification to make it switch to the next desktop
You may want to check out more Mac applications, such as Bulldog, Script Timer or Launch!, which might be similar to ShadowBook.