The rise of cryptocurrencies like Bitcoin has sparked excitement and considerable research in blockchain technology. However, the high power consumption of traditional blockchains makes them unfit for low power IoT devices operating with little to no infrastructure. We present Vegvisir - the first partition-tolerant blockchain suitable for the IoT space. Because of its proof-of-witness concept (as opposed to proof-of-work in other blockchains) and its implementation using conflict-free replicated data types (CRTDs), Vegvisir provides an eventually consistent tamper-proof log with minimal storage and connection requirements. Simulations of Vegvisir's reconciliation protocols show promise for deployment in IoT devices, with applications across various environments such as disaster preparedness and digital agriculture.