diff --git a/shiftregister/app/migrations/0004_shiftregistration_reminder_sent.py b/shiftregister/app/migrations/0004_shiftregistration_reminder_sent.py
new file mode 100644
index 0000000..f99e618
--- /dev/null
+++ b/shiftregister/app/migrations/0004_shiftregistration_reminder_sent.py
@@ -0,0 +1,18 @@
+# Generated by Django 4.0.4 on 2022-04-20 17:57
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("app", "0003_message_created_at"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="shiftregistration",
+            name="reminder_sent",
+            field=models.BooleanField(default=False),
+        ),
+    ]
diff --git a/shiftregister/app/models.py b/shiftregister/app/models.py
index 108c95a..61b96bd 100644
--- a/shiftregister/app/models.py
+++ b/shiftregister/app/models.py
@@ -68,10 +68,24 @@ class ShiftRegistration(models.Model):
     # use restrict for now as Model.delete is not called
     shift = models.ForeignKey(Shift, on_delete=models.RESTRICT)
     helper = models.ForeignKey(Helper, on_delete=models.CASCADE)
+    reminder_sent = models.BooleanField(default=False)
 
     def can_cancel(self):
         return self.shift.start_at > (timezone.now() + timedelta(hours=4))
 
+    def send_reminder(self):
+        text = f"Deine Kontakt-Schicht begint um {self.shift.start_at.strftime('%H:%M')}, bitte komme eine halbe Stunde vorher an den Infopoint."
+        msg = Message(to=self.helper, text=text)
+        msg.save()
+        self.reminder_sent = True
+        self.save()
+
+    def get_unnotified_registrations():
+        return ShiftRegistration.objects.filter(
+            reminder_sent=False,
+            shift__start_at__lte=timezone.now() + timedelta(minutes=60),
+        )
+
 
 class Message(models.Model):
     # remove limit and send long messages in multiple messages?