Instead of having to monitor a print by periodically checking through a webcam or in person, why not use the IR height sensor to analyze a print in progress?
The print head will be moving over a part as it prints (duh). Capture the data from the height sensor simultaneously and compare it to the GCODE. If the height sensor begins to report values beyond a set threshold where there should be material printed, automatically pause the machine and email an alert. The precise offset of the height sensor from the nozzle could be found by printing a shape in the center of the bed and scanning over it afterwards.
If you really wanted to be fancy, stream the data to a PC, generate a point cloud, create a mesh from it, and compare the result to the original model.