I don't have a block heater on my L3901DT yet, but when I drove my Ram with a Cummins everyday, I wrote a script to turn on an X10 outlet that the block heater was plugged into on at different times based on the outside temperature. I have multiple temperature sensors, one of them is the outside temperature. When I got home each night when I knew the temperature might get below 40F I would plug the block heater into the X10 outlet. The script runs everyday even if the truck wasn't plugged in, that way I wouldn't forget to start it each night. I would leave the house at 6:30, so here is what the script did:
At 4:00 if it is 10F or lower turn on outlet
At 4:30 if it is 20F or lower turn on outlet
At 5:00 if it is 30F or lower turn on outlet
At 5:30 if it is 40F or lower turn on outlet
At 7:00 turn outlet off:
I plan on having an X10 controlled outlet in the shed where the tractor is and on days that I plan on using it and it is cold outside I will turn it on based on the temperature.
You can do the same thing with an X10 outlet and a remote control like jajiu is doing. I just happen to be a little bit of a geek.