Wireless links using backscatter communication offer the advantages of reduced complexity and orders of magnitude lower power consumption than active radios. However, the need for specialized receiver systems has limited the use of backscatter in wireless sensing applications. To address this need, we introduce the first backscatter-based wireless sensor tag that can stream sensor data to any of the billions of existing Bluetooth 4.0 Low Energy (BLE) devices, including smartphones, tablets, and PCs. The FPGA-based “BLE Backscatter Sensor Node” (BBSN) uses an external carrier source and requires no modifications to smartphone, tablet, or PC hardware or software whatsoever. The device transmits a 1.0 Mbps data stream with BLE-compatible frequency-shift keying modulation. The backscatter modulator consumes only 158 pJ/bit, making it over 60X more energy efficient than a conventional BLE active radio (>10 nJ/bit).