This study introduces the Wheelchair-Mountable Robotic Arm (WMRA), a cost-effective assistive device engineered to expand the functional independence of wheelchair users. Distinct from existing designs that rely on expensive powered wheelchairs, the proposed WMRA is specifically developed to be compatible with standard, low-cost hospital-use wheelchairs—those most commonly available in clinical and caregiving environments. The system employs a hydraulic Electro-Hydraulic Actuator (EHA) to deliver robust and responsive motion control, while its mechanical configuration ensures that primary userfacing joints retain their posture even during power interruptions, improving safety in practical use. Design validation confirms that the WMRA achieves a functional working range extending from ground level to 1805 mm—the height of an average ordering kiosk—while reliably supporting a payload of 5 kg. Mechanical testing further verifies a peak torque of 65.86 Nm at Joint 1, ensuring stable manipulation of commonly handled objects. Simulation environments including ROS 2 with Gazebo and NVIDIA Omniverse Isaac Sim were employed to evaluate system integrity and task feasibility prior to physical prototyping.