Real-time network measurements can be used to improve performance of existing Internet services and support the deployment of new services dependent on performance information (e.g., topologicallyaware overlay networks). Internet-wide measurement faces numerous scaling-related challenges, including the problem of deploying enough measurement endpoints for wide-spread coverage. We observe that peerto- peer networks, made up of “volunteer” hosts around the Internet world, have the potential to provide a level of coverage that greatly exceeds that made possible with the tedious human process of negotiating endpoint locations. We therefore propose a distributed peer-to-peer system that can be queried for network performance information. We sketch the architecture and operation of such a system and briefly relate it to alternative proposals for measurement infrastructures. Finally, we list open problems related to the design and realization of such a system.