This graphical 128x64 LCD Controller is the perfect add-on for your RepRap Printer.
This simple addition gives you the following features:
You can connect it to your RAMPS board using the included adapter. This is still a relaitvely new option currently support for all features is built-in to Marlin firmare.
After connecting this panel to your controller and configuring the controller firmware you can print without your pc, the Smart Controller supplies power for your SD card. Further more all actions like calibration, axes movements can be done using the rotary encoder on the Smart Controller. Print your 3D designs without a PC, just save the g-code program on the SD card.
For controller which already have an SD-card you should continue to use the SD-card slot on the controller.
The reprap.org page with information on how to connect it and set up your firmware to use it is here: