AWS IoT Device Defender adds support for custom metrics

You can now use AWS IoT Device Defender to monitor operational health metrics that are unique to your fleet or use case. For example, you could define a new metric to monitor the memory usage or CPU usage on your devices. After your devices start sending these metrics to the cloud, you can monitor the metrics and trigger alarms when memory usage exceeds expected ranges or when CPU usage exceeds a statistically significant threshold. The alerts can be viewed in the Device Defender console or shared through AWS Simple Notification Service (SNS). 

Source:: Amazon AWS