Significant obstacles persist in meeting the accessibility needs of computer and smartphone users with mild-to-moderate upper limb motor impairments as they use their devices at work and home. Multimodal input can help, but has not been widely adopted. We build on existing literature with a discovery survey and semistructured follow-up interviews in which we identify common themes related to the limitations of today’s solutions and the ad hoc workarounds which are adopted. We ran a series of co-design workshop sessions to understand the potential of modern “physical computing” electronic device prototyping technologies to provide new and effective input options for our target user base. We present the resulting prototype solutions and describe the technology choices made. Finally, we discuss how the co-design process, in conjunction with access to suitable physical prototyping technologies, can be a powerful approach for designing accessibility-focused input systems.