diff --git a/aprslib/packets/telemetry.py b/aprslib/packets/telemetry.py
index b0e4d1d..b1cf22c 100644
--- a/aprslib/packets/telemetry.py
+++ b/aprslib/packets/telemetry.py
@@ -1,7 +1,10 @@
+from aprslib import string_type
 from aprslib.packets.base import APRSPacket
 
 __all__ = [
     'TelemetryReport',
+    'TelemetryUnit',
+    'TelemetryParm',
 ]
 
 class TelemetryAddon(object):
@@ -9,7 +12,6 @@ class TelemetryAddon(object):
     _sequence_number = 0
     _digital_value = 0
 
-
     def __init__(self, *args, **kwargs):
         self._analog_values = AnalogValueList()
         super(TelemetryAddon, self).__init__( *args, **kwargs)
@@ -81,10 +83,27 @@ class AnalogValueList(ImmutableList):
     def __setitem__(self, i, v):
         if not 0 <= i <= 4:
             raise IndexError("Index outside of range 0-4, got %d" % i)
-        if not 0 <= v <= 999:
+        if not isinstance(v, int) or not 0 <= v <= 999:
             raise ValueError("Value outside of range 0-999, got %d" % v)
-        else:
-            list.__setitem__(self, i, v)
+
+        list.__setitem__(self, i, v)
+
+
+class UnitParmList(ImmutableList):
+    _lengths = (7, 7, 6, 6, 5, 6, 5, 4, 4, 4, 3, 3, 3)
+
+    def __init__(self):
+        list.__init__(self, [''] * 13)
+
+    def __setitem__(self, i, v):
+        if not 0 <= i <= 12:
+            raise IndexError("Index outside of range 0-12, got %d" % i)
+        if not isinstance(v, string_type):
+            raise TypeError("Expected type to be str, got %s" % type(v))
+        if len(v) > self._lengths[i]:
+            raise ValueError("Expected length index %d is %d, got %d" % (i, self._lengths[i], len(v)))
+
+        list.__setitem__(self, i, v)
 
 
 class TelemetryReport(TelemetryAddon, APRSPacket):
@@ -113,3 +132,75 @@ class TelemetryReport(TelemetryAddon, APRSPacket):
             self.digital_value,
             self.comment,
             )
+
+class TelemetryMessage(APRSPacket):
+    format = 'telemetry-messsage'
+    addressee = 'N0CALL'
+
+    def _serialize_body(self):
+        return ":{: <9s}:".format(self.addressee)
+
+class TelemetryUnit(TelemetryMessage):
+    _tUNIT = None
+
+    def __init__(self, *args, **kwargs):
+        self._tUNIT = UnitParmList()
+        super(TelemetryUnit, self).__init__( *args, **kwargs)
+
+    @property
+    def tUNIT(self):
+        return self._tUNIT
+
+    @tUNIT.setter
+    def tUNIT(self, v):
+        if not isinstance(v, list):
+            raise TypeError("Expected analog_values to be list, got %s" % type(v))
+        if len(v) != 13:
+            raise ValueError("Expected a list of 13 elements, got a list of %d" % len(v))
+
+        for i, elm in enumerate(v):
+            self._tUNIT[i] = elm
+
+    def _serialize_body(self):
+        last = 0
+        for i, elm in enumerate(self.tUNIT):
+            if elm: last = i
+
+        return "{:s}{:s}{:s}".format(
+            TelemetryMessage._serialize_body(self),
+            'UNIT.',
+            ','.join(self.tUNIT[:last+1]),
+            )
+
+
+class TelemetryParm(TelemetryMessage):
+    _tPARM = None
+
+    def __init__(self, *args, **kwargs):
+        self._tPARM = UnitParmList()
+        super(TelemetryParm, self).__init__( *args, **kwargs)
+
+    @property
+    def tPARM(self):
+        return self._tPARM
+
+    @tPARM.setter
+    def tPARM(self, v):
+        if not isinstance(v, list):
+            raise TypeError("Expected analog_values to be list, got %s" % type(v))
+        if len(v) != 13:
+            raise ValueError("Expected a list of 13 elements, got a list of %d" % len(v))
+
+        for i, elm in enumerate(v):
+            self._tPARM[i] = elm
+
+    def _serialize_body(self):
+        last = 0
+        for i, elm in enumerate(self.tPARM):
+            if elm: last = i
+
+        return "{:s}{:s}{:s}".format(
+            TelemetryMessage._serialize_body(self),
+            'PARM.',
+            ','.join(self.tPARM[:last+1]),
+            )