A common scenario for sensor networks is data-gathering: nodes gather data (periodically, or triggered by certain conditions) and send it back to a sink (or basestation). Data is sent over multiple hops, using a tree topology. Such a system with a single sink presents scaling difficulties as the network grows: the average distance to the sink increases, and nodes near the top of the tree must relay a disproportionate amount of traffic. Placing multiple sinks (basestations) can alleviate this, but on the other hand introduces additional overhead if all sinks flood the entire network. Voronoi scoping is a simple distributed technique to limit floods so that each flood reaches only the subset of nodes in the originating sinks region; that is the nodes who have the originator as closest sink. We have implemented the algorithm in one-phase pull; this demo uses emview to visualize in real-time the clusters formed in the LECS lab ceiling array of motes.