Monitoring X, Y, Z position of extruder in real time
Depending on your methods, you can easily (evidently) get (or compute) "where the printhead is commanded to be" in more-or-less real time, as evidenced by the "progress display" in Repetier Host software (based off the G-Code it's sending to the printer) - though I have found it advisable to stick with the temperature display while printing as I've had the host bog down on processing the display at least once, which then made the print go slow.

As for "is it even possible" - sure, how much would you like to spend? Add encoders to each axis that are read by the computer, or by something (probably not your printer processor for "least impact on the printing" and "most real-time") that reads them and talks to the computer. The more precise you need, the more expensive it gets. Of course that also starts to probe 'what you mean by "real time" ?' as there are applications where the time spent reading the encoder and sending/receiving the data would be considered "not real-time" by the time the computer had the data, but for the average person with a printer built partly from wood, it's likely "real-time enough."