In order to create a generic monitor type that is based off a PowerShell DS, you may need to parameterize not only the operators within expression filters but parameterize the name of the name/value pair coming back from the property bag in your PS script.
Notice the UnhealthyOperator as well as the HealthyOperator specified within the configuration for the monitor type are of type CriteriaCompareType. In order to access the type, the ExpressionEvaluatorSchema needs to be included. Also, notice the Variable configuration element is meant to be the name of the value being passed back from the PS script which needs to be ran through the ExpressionFilter. The ExpressionFilter is then populated using the $Config variables. Here is a potential ConditionDetection for a healthy state:
Here is the resulting monitor:
The monitor would raise an alert if the random number returned from the script is <=5.