The key challenges of local sensor networks are in supporting high sensor density, information security, physical size, and especially energy efficiency at a level that could eliminate the need for batteries or external power supplies. This article presents a novel scheme that answers all issues at the cost of minor information losses in low data rate applications that tolerate latency. Experimental verification is made using a sensor node implemented on a flexible electronics platform. Lightly encrypted data are transmitted by embedding it into Bluetooth advertising packets, contributing to ultralow-energy wireless power consumption, and theoretically enabling an unlimited number of nodes in the local network. In the experiments, the energy dissipation per transmitted 14-B information packet varied between 19.83 and 105.93 mu text{W} depending on the system configuration, while the data loss rates ranged from 7.4% to 0.004%, respectively. As the flexible substrate can be attached to various surfaces, the applications extend from wearable to industrial condition monitoring devices.