diff --git a/z_server/devices/__init__.py b/z_server/devices/__init__.py
index e037358..5ddd436 100644
--- a/z_server/devices/__init__.py
+++ b/z_server/devices/__init__.py
@@ -34,15 +34,17 @@ class base(object):
         logger.debug("Target value for device identified: %s: %s", key, repr(value))
 
     def state(self, key, value):
-        self.__state_storage__[key] = value
+        self.__state_storage__[key] = time.time(), value
         logger.debug("Device state identified: %s: %s", key, repr(value))
 
     def status(self, key):
+        tm_s, value_s = self.__state_storage__.get(key, (0, None))
         try:
             tm_t, value_t = self.__target_storage__[key]
-            value_s = self.__state_storage__.get(key)
         except KeyError:
-            return {"status": nagios.Nagios.UNKNOWN, "msg": "Device exists, but no setpoint change or unknown monitoring"}
+            if value_s is not None:
+                return {"status": nagios.Nagios.WARNING, "msg": "Current temperature setpoint %.1f°C (age=%.1fs), but never received a setpoint" % (value_s, time.time()-tm_s)}
+            return {"status": nagios.Nagios.UNKNOWN, "msg": "Device exists, but no data received or unknown monitoring"}
         else:
             tm = time.time()
             dt = tm - tm_t