Wyze Cams have the ability to listen for the distinct signature sound of a Smoke Detector or a Carbon Monoxide Detector. This is a feature that is available on the cam out of the box and is not limited by subscription or any other equipment.
To use this, enter the Cam Settings 
, Alarm Settings. There you will find the toggles for Smoke Alarm Sound and CO Alarm Sound. When activated, it will upload a 12s video from the cam and send a Push Notification to the phone. Notifications for the cam, the app, and the phone must be enabled.
The Cam’s programmed ability to do this is not limited or restricted by the HMS Hub’s ability to do the same. The feature on the HMS Hub is somewhat of a redundant alert for those who subscribe to the HMS. It uses the Cam’s resident ability to listen for the distinct sound of a Smoke\CO alarm to do this.
It does require an HMS subscription as the settings for the feature are found within the Monitoring Tab>Home Monitoring Settings>Security Cameras. This menu cannot be accessed without a subscription.
The HMS Smoke\CO Alert Notification cannot trigger a monitored Alarm Response. It will not alert Noonlight and no Fire\Police will be notified.
For the HMS to use its Smoke\CO Alarm feature, the cam must be added to as one of the 5 Security Cams within the HMS. Opening the cam from within the Security Cam menu reveals the toggles to turn this on.
The Push Notification Alert sent by the HMS is a different Threat Alert notification than the Push Notification Alert sent by the Cam. With both enabled, you should theoretically get two push notifications if the settings are enabled for both.
Wyze does not sell any standalone Smoke\CO detector\sensor or one that will pair with the Sense Hub. It has been requested by users many times in the Wishlist.