Best alternative to Stop an Activity started from a Service

I started an activity with the following code from my service:

Intent cmActivityIntent = new Intent(getApplicationContext(), CallManagementActivity.class);
cmActivityIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(cmActivityIntent);

In the app's manifest the launchMode of the activity is defined as android:launchMode="singleTask".

I've been looking for ways of stopping the activity on the service's onDestroy() but I haven't been able to find any documentation that can help me. And I've only found one way of doing it.

I've seen the aproach of checking on the serviceif the activity is instanced using an activity-class-static-property (public static boolean isInstanced) and sending another intent to the activity with a FINISH_ACTIVITY extra if it is. Then, on the activity's onNewIntent() the flag would be checked and the activity would be finished if the flag was included.

This approach doesn't feel right to me, since intents are supposed to be used start activities and not stopping them.

Does someone know any other way of how to acomplish this?