Alot of the functionality where you needed measures in AppMon is already there out of the box with Dynatrace. For other Use Cases you can define Request Attributes in Dynatrace.
But there is no custom alerting based on what where measures in Dynatrace. Dynatrace automatically detects problems by evaluating against baselines. If needed you can adjust thresholds or in some cases set hard limits.
Can you tell us more about your specific Use Case?