Vetus Exhaust Temperature Alarm - Black, 12V XHI12B New, never used.  Has both visual and audible alert to exhaust temperature exceeding what is normal.  Requires a sensor, which is not included (they are sold separately by Vetus and others).  Sensor can be any brand and attach to wet exhaust in a variety of ways.  Some are strapped around the exhaust hose, some are installed in the exhaust hose or water-lift muffler.  That sensor is simply a switch that closes a circuit and activates this display/alarm when temperatures exceed limits.  Comes with both black and chrome bezels.  New condition.  This unit is $90+ retail.