After seeing the design in
http://www.thingiverse.com/thing:1646220

i set myself to remix it to add the following

Bracket to mount it to my frame

Oil can to lubricate filament as it passes through ...

Just enable the setting in marlin and connect to D4 on Ramps

This thing was made with Tinkercad. Edit it online https://www.tinkercad.com/things/bZxfQronhsI