PlaiPin is a wearable plush robot companion and a protocol that emerges embodied social interaction with decentralized digital identity, allowing agent-to-agent transactions via proximity. When two PlaiPins pass by physically, the PlaiPin Inter-Companion Protocol (PICP) provides consented discovery, mutual authentication and micro-messages, allowing new ways of discoverability and exchange of information beyond the subject-matter rails. PlaiPin is built as an open framework with a mini-app store where any creator or project can develop custom companions, voices, and programs. We provide the hardware infrastructure; developers build the experiences. Think App Store, but for physical AI companions. Imagine companions that identify frequent contacts, swap gifts based on interests, maintain memory across encounters, facilitate peer-to-peer value exchange, localized edge computing and transferable embodiment all happening autonomously in the background as you move through the world.