The Signpost platform enables easily-deployable city-scale sensing. Signposts can be mounted to any sign post, harvest solar energy, and provide the key services for their pluggable sensor modules to perform sensing tasks. To enable multiple non-aligned sensor modules to operate within the resource constraints of the system, Signposts meter resource utilization and isolate sensor modules that use over their fair share. We have created sensor modules for audio volume, rf spectrum, radar-based motion, and ambient environmental sensing. The platform is currently being deploying on UC Berkeley's campus, and we hope to use it as a platform to test distributed, resource constrained, software and hardware systems.