Yes it's possible. I haven't done it though, sorry no first hand experience here. If I were to do it I would replace a freeze plug with a heater.
There are many ways to skin that cat. Oil pan heater, dip stick heater, and if you live where it's really cold there is a heater that goes into the middle of the heater hose that will circulate warm water throughout the engine and heater coil. This will raise the temp inside of the car (somewhat) as well as heat the engine. It's nice for the heater to work as soon as the car is started.
What I do with my Diesel truck is to use a high amp timer (get it at Walmart or someplace similar, made for coffee pots) to turn on the block heater a couple of hours before I start it. Just remember to route the plug in such a way that no damage will be done when you forget to unplug it and drive away.
With aircraft you don't want to leave the heater on for extended periods as the warm engine will get condensation (which causes rust and breaks down the oil) in it. I assume it would be the same for automobiles