Spatial Computing (SC) is an emerging paradigm that interlaces virtual 3D environments with physical ones, promising advancements in communication, teleoperation, education, and training. Despite its potential, accessibility of SC experiences across platforms is still a challenge. Virtual environments can be experienced using a diverse array of hardware interfaces, from conventional screens and keyboards to immersive head-mounted displays (HMDs) and full-body tracking suits, and these varying input modalities necessitate extra development efforts to maintain seamless user interaction across different devices and platforms. This paper introduces a concept of “Presence Drivers” (PDs), which offers a unified user representation for SC applications, independent of specific input devices. PDs function as a direct connection layer between the user's body and the SC application, simplifying the development of adaptive, user-friendly spatial software. The article discusses the PD concept within the current technological landscape, outlines its architecture, and proposes a reference implementation using Unity engine.