If you run long-running print jobs or use expensive filament, having a print failure caused by filament feeding problems can be a very frustrating and expensive experience!
I've certainly had my fair share of print jobs that turned into air prints when I under-estimated the amount of remaining filament on the spool!
Aaron Tunell developed a filament monitor that detects feeding problems and puts the printer into P-stop (Pause) before the job is lost from air printing!
We have a limited supply of his monitor available on our site. Please see the product detail page for more information.