diff --git a/README.md b/README.md
index b1c82e4..561bcee 100644
--- a/README.md
+++ b/README.md
@@ -57,6 +57,14 @@ Instead of manually editing your crontab, this project provides a simple GraphQL
 
 ### Example API Usage
 
+**Check if alarm is currently ringing:**
+```graphql
+query {
+  isRinging
+}
+```
+Returns `true` if the wecker alarm clock is currently active (playing music), `false` otherwise.
+
 **Get all alarms:**
 ```graphql
 query {
@@ -92,6 +100,15 @@ mutation {
 ```
 
 
+### Example response for `isRinging`:
+```json
+{
+  "data": {
+    "isRinging": true
+  }
+}
+```
+
 ## How the Puzzle Works
 1. **Ringing:** The music plays in an endless loop.
 2. **Start:** Press the arcade button once to start the puzzle. Wait 3 seconds.
diff --git a/api/schema.py b/api/schema.py
index e7c311d..5545012 100644
--- a/api/schema.py
+++ b/api/schema.py
@@ -4,6 +4,7 @@ import os
 import sys
 from pathlib import Path
 from api.crontab_manager import CrontabManager
+from common import PID_FILE
 
 
 def get_manager():
@@ -11,6 +12,20 @@ def get_manager():
     return CrontabManager(tabfile=tabfile)
 
 
+def is_wecker_ringing() -> bool:
+    """Check if the wecker process is currently running via the PID file."""
+    if not os.path.exists(PID_FILE):
+        return False
+    try:
+        pid: int
+        with open(PID_FILE) as f:
+            pid = int(f.read().strip())
+        os.kill(pid, 0)
+        return True
+    except (ValueError, ProcessLookupError, PermissionError, OSError):
+        return False
+
+
 @strawberry.type
 class Alarm:
     id: str
@@ -21,6 +36,10 @@ class Alarm:
 
 @strawberry.type
 class Query:
+    @strawberry.field
+    def is_ringing(self) -> bool:
+        return is_wecker_ringing()
+
     @strawberry.field
     def get_alarms(self) -> List[Alarm]:
         manager = get_manager()
diff --git a/common.py b/common.py
new file mode 100644
index 0000000..2637cde
--- /dev/null
+++ b/common.py
@@ -0,0 +1,5 @@
+from pathlib import Path
+
+# The PID file path — defined once here to avoid duplication.
+# wecker.py writes this file when it starts; api/schema.py reads it to check state.
+PID_FILE = str(Path(__file__).parent.absolute() / "wecker.pid")
\ No newline at end of file
diff --git a/tests/test_api.py b/tests/test_api.py
index 7448b4d..9050382 100644
--- a/tests/test_api.py
+++ b/tests/test_api.py
@@ -1,3 +1,4 @@
+from unittest.mock import patch
 from fastapi.testclient import TestClient
 import tempfile
 import os
@@ -14,6 +15,33 @@ from api.main import app  # noqa: E402
 client = TestClient(app)
 
 
+def test_is_ringing_returns_false_when_not_running():
+    """Test that isRinging returns False when no wecker process is running."""
+    headers = {"X-API-Key": "test-secret"}
+    query = """
+    query {
+      isRinging
+    }
+    """
+    res = client.post("/graphql", json={"query": query}, headers=headers)
+    assert res.status_code == 200
+    assert res.json()["data"]["isRinging"] is False
+
+
+@patch("api.schema.is_wecker_ringing", return_value=True)
+def test_is_ringing_returns_true_when_running(mock_is_ringing):
+    """Test that isRinging returns True when a wecker process is running."""
+    headers = {"X-API-Key": "test-secret"}
+    query = """
+    query {
+      isRinging
+    }
+    """
+    res = client.post("/graphql", json={"query": query}, headers=headers)
+    assert res.status_code == 200
+    assert res.json()["data"]["isRinging"] is True
+
+
 def test_auth_missing():
     query = """
     query {
@@ -173,3 +201,13 @@ def test_graphql_workflow():
     # 7. List again is empty
     res = client.post("/graphql", json={"query": query_get}, headers=headers)
     assert res.json()["data"]["getAlarms"] == []
+
+
+def test_pid_file_same_shared_constant_in_api():
+    """Ensure api.schema uses the same PID_FILE from common, not a redefinition."""
+    from api import schema as api_schema
+    import common
+
+    assert api_schema.PID_FILE is common.PID_FILE, (
+        "api.schema.PID_FILE must reference common.PID_FILE, not redefine it"
+    )
diff --git a/tests/test_single_instance.py b/tests/test_single_instance.py
index 4dca977..c87980b 100644
--- a/tests/test_single_instance.py
+++ b/tests/test_single_instance.py
@@ -1,7 +1,7 @@
-import os
-import sys
 import pytest
-from unittest.mock import MagicMock, patch
+from unittest.mock import patch
+
+import common
 import wecker
 
 # We need to mock the PID file existence and os.kill to test the logic
@@ -80,3 +80,17 @@ def test_remove_pid_file_wrong_pid(mock_pid_file):
         
         wecker.remove_pid_file()
         assert mock_pid_file.exists()
+
+
+def test_pid_file_defined_once_across_modules():
+    """
+    DRY principle: PID_FILE must be defined in common.py and imported by
+    both wecker.py and api/schema.py — not redefined in each.
+    """
+    # wecker.py imports PID_FILE from common — verify it's the same object
+    assert wecker.PID_FILE is common.PID_FILE, (
+        "wecker.PID_FILE must reference common.PID_FILE, not redefine it"
+    )
+
+    # Verify the path ends with "wecker.pid"
+    assert common.PID_FILE.endswith("wecker.pid")
diff --git a/wecker.py b/wecker.py
index a6b0439..38deeb4 100644
--- a/wecker.py
+++ b/wecker.py
@@ -6,6 +6,8 @@ import random
 import sys
 import os
 
+from common import PID_FILE
+
 # Configure logging
 logging.basicConfig(
     level=logging.INFO,
@@ -13,8 +15,6 @@ logging.basicConfig(
     handlers=[logging.FileHandler("wecker.log"), logging.StreamHandler()],
 )
 
-PID_FILE = "wecker.pid"
-
 
 def ensure_single_instance():
     """Ensures that only one instance of the script is running."""