Heater wattage reporting for M105 using EXTRUDER_WATTS and BED_WATTS

Marlin/Configuration.h

 // HEATER_BED_DUTY_CYCLE_DIVIDER intervals.
 //#define HEATER_BED_DUTY_CYCLE_DIVIDER 4
 
+// If you want the M105 heater power reported in watts, define the BED_WATTS, and (shared for all extruders) EXTRUDER_WATTS 
+//#define EXTRUDER_WATTS (12.0*12.0/6.7) //  P=I^2/R 
+//#define BED_WATTS (12.0*12.0/1.1)      // P=I^2/R
+
 // PID settings:
 // Comment the following line to disable PID and enable bang-bang.
 #define PIDTEMP

Marlin/Marlin_main.cpp

       #endif
 
         SERIAL_PROTOCOLPGM(" @:");
+      #ifdef EXTRUDER_WATTS
+        SERIAL_PROTOCOL((EXTRUDER_WATTS * getHeaterPower(tmp_extruder))/127);
+        SERIAL_PROTOCOLPGM("W");
+      #else
         SERIAL_PROTOCOL(getHeaterPower(tmp_extruder));
+      #endif
 
         SERIAL_PROTOCOLPGM(" B@:");
+      #ifdef BED_WATTS
+        SERIAL_PROTOCOL((BED_WATTS * getHeaterPower(-1))/127);
+        SERIAL_PROTOCOLPGM("W");
+      #else
         SERIAL_PROTOCOL(getHeaterPower(-1));
+      #endif
 
         #ifdef SHOW_TEMP_ADC_VALUES
           #if defined(TEMP_BED_PIN) && TEMP_BED_PIN > -1