tl;dr: QuadRF is an open-source handheld phased-array SDR (4.9-6 GHz) built on a Raspberry Pi 5 and FPGA, streaming I/Q data over the Pi's MIPI lanes at 5+ Gbps. In hands-on testing it successfully visualized WiFi networks through walls and tracked a DJI drone in flight via an AR overlay, though the UI is still rough. It's a scaled-down piece of a larger project aiming to chain modules for Earth-Moon-Earth radio experiments, currently crowdfunding on Crowd Supply starting at $499.