diff --git a/app/src/main/AndroidManifest.xml b/app/src/main/AndroidManifest.xml
index 0c46d28..08b0af2 100644
--- a/app/src/main/AndroidManifest.xml
+++ b/app/src/main/AndroidManifest.xml
@@ -8,7 +8,7 @@
   <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
 
   <application
-      android:name=".App"
+      android:name=".NockNockApp"
       android:allowBackup="true"
       android:icon="@mipmap/ic_launcher"
       android:label="@string/app_name"
diff --git a/app/src/main/java/com/afollestad/nocknock/AppExt.kt b/app/src/main/java/com/afollestad/nocknock/AppExt.kt
new file mode 100644
index 0000000..fa42732
--- /dev/null
+++ b/app/src/main/java/com/afollestad/nocknock/AppExt.kt
@@ -0,0 +1,38 @@
+/*
+ * Licensed under Apache-2.0
+ *
+ * Designed and developed by Aidan Follestad (@afollestad)
+ */
+package com.afollestad.nocknock
+
+import android.app.Activity
+import android.app.Application
+import android.app.Application.ActivityLifecycleCallbacks
+import android.os.Bundle
+
+typealias ActivityLifeChange = (activity: Activity, resumed: Boolean) -> Unit
+
+/** @author Aidan Follestad (afollestad) */
+fun Application.onActivityLifeChange(cb: ActivityLifeChange) {
+  registerActivityLifecycleCallbacks(object : ActivityLifecycleCallbacks {
+    override fun onActivitySaveInstanceState(
+      activity: Activity?,
+      outState: Bundle?
+    ) = Unit
+
+    override fun onActivityPaused(activity: Activity) = cb(activity, false)
+
+    override fun onActivityResumed(activity: Activity) = cb(activity, true)
+
+    override fun onActivityStarted(activity: Activity) = Unit
+
+    override fun onActivityDestroyed(activity: Activity) = Unit
+
+    override fun onActivityStopped(activity: Activity) = Unit
+
+    override fun onActivityCreated(
+      activity: Activity?,
+      savedInstanceState: Bundle?
+    ) = Unit
+  })
+}
diff --git a/app/src/main/java/com/afollestad/nocknock/App.kt b/app/src/main/java/com/afollestad/nocknock/NockNockApp.kt
similarity index 57%
rename from app/src/main/java/com/afollestad/nocknock/App.kt
rename to app/src/main/java/com/afollestad/nocknock/NockNockApp.kt
index db2842b..c6eab86 100644
--- a/app/src/main/java/com/afollestad/nocknock/App.kt
+++ b/app/src/main/java/com/afollestad/nocknock/NockNockApp.kt
@@ -6,23 +6,35 @@
 package com.afollestad.nocknock
 
 import android.app.Application
-import android.app.NotificationManager
-import android.app.job.JobScheduler
-import android.content.Context
+import android.util.Log
 import com.afollestad.nocknock.di.AppComponent
 import com.afollestad.nocknock.di.DaggerAppComponent
 import com.afollestad.nocknock.engine.statuscheck.BootReceiver
 import com.afollestad.nocknock.engine.statuscheck.CheckStatusJob
+import com.afollestad.nocknock.notifications.NockNotificationManager
 import com.afollestad.nocknock.ui.AddSiteActivity
 import com.afollestad.nocknock.ui.MainActivity
 import com.afollestad.nocknock.ui.ViewSiteActivity
 import com.afollestad.nocknock.utilities.Injector
+import com.afollestad.nocknock.utilities.ext.systemService
 import okhttp3.OkHttpClient
+import javax.inject.Inject
 
 /** @author Aidan Follestad (afollestad) */
-class App : Application(), Injector {
+class NockNockApp : Application(), Injector {
 
-  lateinit var appComponent: AppComponent
+  companion object {
+    private fun log(message: String) {
+      if (BuildConfig.DEBUG) {
+        Log.d("NockNockApp", message)
+      }
+    }
+  }
+
+  private lateinit var appComponent: AppComponent
+  @Inject lateinit var nockNotificationManager: NockNotificationManager
+
+  private var resumedActivities: Int = 0
 
   override fun onCreate() {
     super.onCreate()
@@ -36,15 +48,26 @@ class App : Application(), Injector {
           chain.proceed(request)
         }
         .build()
-    val jobScheduler = getSystemService(Context.JOB_SCHEDULER_SERVICE) as JobScheduler
-    val notificationManager = getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
 
     appComponent = DaggerAppComponent.builder()
         .application(this)
         .okHttpClient(okHttpClient)
-        .jobScheduler(jobScheduler)
-        .notificationManager(notificationManager)
+        .jobScheduler(systemService(JOB_SCHEDULER_SERVICE))
+        .notificationManager(systemService(NOTIFICATION_SERVICE))
         .build()
+    appComponent.inject(this)
+
+    onActivityLifeChange { activity, resumed ->
+      if (resumed) {
+        resumedActivities++
+        log("Activity resumed: $activity, resumedActivities = $resumedActivities")
+      } else {
+        resumedActivities--
+        log("Activity paused: $activity, resumedActivities = $resumedActivities")
+      }
+      check(resumedActivities >= 0) { "resumedActivities can't go below 0." }
+      nockNotificationManager.setIsAppOpen(resumedActivities > 0)
+    }
   }
 
   override fun injectInto(target: Any) = when (target) {
diff --git a/app/src/main/java/com/afollestad/nocknock/di/AppComponent.kt b/app/src/main/java/com/afollestad/nocknock/di/AppComponent.kt
index f6bd78f..84534a9 100644
--- a/app/src/main/java/com/afollestad/nocknock/di/AppComponent.kt
+++ b/app/src/main/java/com/afollestad/nocknock/di/AppComponent.kt
@@ -8,6 +8,7 @@ package com.afollestad.nocknock.di
 import android.app.Application
 import android.app.NotificationManager
 import android.app.job.JobScheduler
+import com.afollestad.nocknock.NockNockApp
 import com.afollestad.nocknock.engine.EngineModule
 import com.afollestad.nocknock.engine.statuscheck.BootReceiver
 import com.afollestad.nocknock.engine.statuscheck.CheckStatusJob
@@ -33,6 +34,8 @@ import javax.inject.Singleton
 )
 interface AppComponent {
 
+  fun inject(app: NockNockApp)
+
   fun inject(activity: MainActivity)
 
   fun inject(activity: ViewSiteActivity)
diff --git a/app/src/main/java/com/afollestad/nocknock/ui/MainActivity.kt b/app/src/main/java/com/afollestad/nocknock/ui/MainActivity.kt
index e292e57..18224fd 100644
--- a/app/src/main/java/com/afollestad/nocknock/ui/MainActivity.kt
+++ b/app/src/main/java/com/afollestad/nocknock/ui/MainActivity.kt
@@ -127,8 +127,6 @@ class MainActivity : AppCompatActivity(), View.OnClickListener {
 
   override fun onResume() {
     super.onResume()
-    notificationManager.setIsAppOpen(true)
-
     val filter = IntentFilter().apply {
       addAction(ACTION_STATUS_UPDATE)
     }
@@ -139,7 +137,6 @@ class MainActivity : AppCompatActivity(), View.OnClickListener {
 
   override fun onPause() {
     super.onPause()
-    notificationManager.setIsAppOpen(false)
     safeUnregisterReceiver(intentReceiver)
   }
 
diff --git a/utilities/src/main/java/com/afollestad/nocknock/utilities/ext/ContextExt.kt b/utilities/src/main/java/com/afollestad/nocknock/utilities/ext/ContextExt.kt
new file mode 100644
index 0000000..9635ad2
--- /dev/null
+++ b/utilities/src/main/java/com/afollestad/nocknock/utilities/ext/ContextExt.kt
@@ -0,0 +1,13 @@
+/*
+ * Licensed under Apache-2.0
+ *
+ * Designed and developed by Aidan Follestad (@afollestad)
+ */
+package com.afollestad.nocknock.utilities.ext
+
+import android.content.Context
+
+/** @author Aidan Follestad (afollestad) */
+inline fun <reified T> Context.systemService(name: String): T {
+  return getSystemService(name) as T
+}