If you are looking for a joystick pendant, there is built in support in Marlin; it just needs to be enabled. All it takes is a 3/4-axis joystick, a push button, and some wiring to hook it up to the Rambo board. The joystick wires directly to the Rambo board along with the enable switch. Then you update Marlin to enable Joystick support, tweak the range values to match your hardware, and it is good to go.
For my MPCNC, I combined a couple approaches using the joystick and an Arduino Nano I had laying around to create my controller. The joystick and enable button are wired up as described above. But I also included an Arduino Nano that is wired to the Serial port of the Rambo and a couple other buttons to allow me to send code commands from the pendant for common setup tasks like homing and resetting coordinates.