This demo presents BlueTag, a permanently deployed underwater sensor system based on backscatter communication. BlueTag is a battery-powered CTD (conductivity, temperature, depth) sensor that transmits measurements every 15 minutes to a remote base station via underwater backscatter. The base station archives these measurements and publishes them online. Unlike prior underwater backscatter systems limited to short-term laboratory experiments, BlueTag has been deployed in the Charles River in Boston, MA since July 9th, 2025, marking the first long-term underwater backscatter deployment of its kind to sense meaningful environmental data. Live data from this deployment is available publicly at https://sk-exp-server.mit.edu/.

Connected devices are becoming more ubiquitous, but powering them remains a challenge. The Wireless Identification and Sensing Platform (WISP) is a fully programmable device capable of energy harvesting and backscatter communication. It can accommodate a variety of sensing modalities and operate without batteries or a wired power supply, making it a suitable device for ubiquitous computing. A new version of WISP is presented. WISP-6.0 is designed to be low-power, modular, and enable dual energy harvesting from sources like a solar panel. Additionally, an upgraded cross-platform host application is built using the latest web technologies. Compared to its predecessor, WISP-5.1, WISP-6.0 consumes 13.62% and 6.29% less power in active accelerometer and active acknowledgment modes respectively. Furthermore, WISP-6.0 is better able to harvest RF energy collected from its antenna, with the greatest improvements at higher input powers.