I found the following on the FAQ section:
How do motion and contact sensors work with Alexa?
Alexa can tell you the current state of your motion and contact sensors. Alexa can also tell you when they change state with a custom message.
Here are some example phrases:
“Alexa, is my front door open?"
“Alexa, is my bedroom window open?”
Alexa can also perform actions when motion is detected or a door/window opens or closes, such as a custom Alexa notification or playing music. Click here to learn more about creating Alexa Routines in the Alexa app.
Can this functionality work directly with an Echo Plus? or do you have to have the SmartThings hub?