Backscatter communications is attractive for its low power requirements due to the lack of actively radiating components; however, commonly used devices are typically limited in range and functionality. Here, we design and demonstrate a backscatter device consisting of a flattened Luneburg lens combined with a spatially-tunable dynamic metasurface. Using quasi-conformal transformation optics (QCTO), we design a flattened, additively manufactured Luneburg lens that focuses incoming waves over a wide field-of-view onto its flattened focal plane. When a reflective surface is placed at the focal plane, the flattened Luneburg lens retroreflects, enabling long-range backscatter communications over an extremely large field-of-view ($\pm30\degree$) and bandwidth. The dynamic metasurface is designed to modulated the reflected phase across the S-band (2-4 GHz) with fine spatial control. Thus, when combined with the flattened Luneburg lens, the device is able to modulate the retroreflected signal to achieve backscatter communications. We experimentally demonstrate full phase control of the backscattered signal across a range of incidence angles, spatial multiplexing, and secure communications against eavesdroppers by actively suppressing or randomizing signals in unwanted directions. The metasurface-backed Luneburg lens device offers a low-power solution for long-range wireless networks with advanced capabilities.