On-body biodesign involves designing with living organisms in direct relation to human bodies and their surrounding ecosystems. Operating within this intimate and dynamic space, the practice creates opportunities by developing novel biotechnologies, cultivating new sensibilities, strengthening ecological literacy, and enabling more attentive and reciprocal coexistence with other living organisms. Yet, given the emerging and cross-disciplinary nature of the field, existing work remains fragmented. How are designers currently biodesigning with, for, and through human bodies, and what design opportunities could emerge for future on-body biodesign? To address these questions, we present a review of 40 artefacts spanning design, art, HCI, and materials science, mapping the design space across three dimensions: the key biological phenomena that enable interactions, the unique experiences these interactions offer, and the ecological configurations through which human bodies, living organisms, and digital technologies interface with one another. With this work, we aim to introduce on-body biodesign as a design research program and offer a structured overview of its current landscape. We further outline potential design pathways, inviting designers to engage with on-body biodesign as a generative space for relational thinking and regenerative practice.