diff --git a/src/lib/services/entities-map.service.ts b/src/lib/services/entities-map.service.ts
index 27790da..bee6608 100644
--- a/src/lib/services/entities-map.service.ts
+++ b/src/lib/services/entities-map.service.ts
@@ -1,6 +1,6 @@
 import { Injectable } from '@angular/core';
-import { BehaviorSubject, Observable, Subject } from 'rxjs';
-import { filter, startWith } from 'rxjs/operators';
+import { BehaviorSubject, Observable, Subject, switchMap } from 'rxjs';
+import { filter, map, startWith } from 'rxjs/operators';
 import { Entity } from '../listing';
 import { RequiredParam, shareLast, Validate } from '../utils';
 import { Id } from '../listing/models/trackable';
@@ -11,6 +11,7 @@ export abstract class EntitiesMapService<Interface, Class extends Entity<Interfa
 
     protected readonly _map = new Map<Id, BehaviorSubject<Class[]>>();
     readonly #entityChanged$ = new Subject<Class>();
+    readonly #entitiesChanged$ = new BehaviorSubject<boolean>(false);
     readonly #entityDeleted$ = new Subject<Class>();
 
     get empty(): boolean {
@@ -68,6 +69,10 @@ export abstract class EntitiesMapService<Interface, Class extends Entity<Interfa
 
         // Emit observables only after entities have been updated
 
+        if(changedEntities.length || deletedEntities.length) {
+            this.#entitiesChanged$.next(true);
+        }
+
         for (const entity of changedEntities) {
             this.#entityChanged$.next(entity);
         }
@@ -105,6 +110,15 @@ export abstract class EntitiesMapService<Interface, Class extends Entity<Interfa
         );
     }
 
+    @Validate()
+    watchChanged$(@RequiredParam() key: Id): Observable<boolean> {
+        return this.#entityChanged$.pipe(
+            startWith(this.get(key)),
+            map(entities => entities as Class[]),
+            map(entities => !!entities.length)
+        );
+    }
+
     watchDeleted$(entityId: Id): Observable<Class> {
         return this.#entityDeleted$.pipe(filter(entity => entity.id === entityId));
     }