diff --git a/billard/admin.py b/billard/admin.py
index f23d77c..b06774c 100644
--- a/billard/admin.py
+++ b/billard/admin.py
@@ -31,8 +31,8 @@ class LocationAdmin(admin.ModelAdmin):
 
 @admin.register(Client)
 class ClientAdmin(admin.ModelAdmin):
-    list_display = ('uuid', 'location', 'report_user')
-    fields = ['location', 'uuid', 'report_user']
+    list_display = ('uuid', 'location', 'report_user', 'last_seen')
+    fields = ['location', 'uuid', 'report_user', 'last_seen']
 
 
 @admin.register(LocationData)
diff --git a/billard/migrations/0026_client_last_seen.py b/billard/migrations/0026_client_last_seen.py
new file mode 100644
index 0000000..d716f52
--- /dev/null
+++ b/billard/migrations/0026_client_last_seen.py
@@ -0,0 +1,17 @@
+# Generated by Django 2.0.2 on 2018-02-11 11:10
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ('billard', '0025_auto_20180211_1059'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='client',
+            name='last_seen',
+            field=models.DateTimeField(blank=True, null=True, verbose_name='Letzter Update'),
+        ),
+    ]
diff --git a/billard/models.py b/billard/models.py
index 45e7378..5ce0cde 100644
--- a/billard/models.py
+++ b/billard/models.py
@@ -52,6 +52,7 @@ class Client(models.Model):
     location = models.ForeignKey(Location, related_name="clients", verbose_name="Standort", on_delete=models.CASCADE)
     report_user = models.ForeignKey(User, blank=True, null=True, verbose_name="Reporting Benutzer",
                                     related_name='reporting_clients', on_delete=models.DO_NOTHING)
+    last_seen = models.DateTimeField(blank=True, null=True, verbose_name="Letzter Update")
 
     def __str__(self):
         return '{}, {}'.format(self.location.name, self.uuid)
diff --git a/billard/templatetags/display_client.py b/billard/templatetags/display_client.py
index e1616d5..d15f81a 100644
--- a/billard/templatetags/display_client.py
+++ b/billard/templatetags/display_client.py
@@ -1,4 +1,4 @@
-from datetime import datetime
+from datetime import datetime, timedelta
 
 from django import template
 from django.utils.html import format_html
@@ -34,6 +34,9 @@ def display_client(client, desk_no):
             prize = '{0:.2f}'.format(prize)
             if prize != a.prize:
                 a.prize = prize
+    before5min = datetime.now() - timedelta(minutes=5)
+    if client.last_seen is not None and client.last_seen < before5min:
+        alert = 'alert-danger'
     html = '<div class="col col-12 col-lg-6">\n'
     html += '    <div class="table-info alert {}">\n'.format(alert)
     html += '        <h4 style="text-align: center">({}) {}</h4>\n'.format(desk_no, desk.name)