Engineers reported a conformal, ultrathin crystalline‑silicon Hall sensor array designed to monitor three‑dimensional tumor tissues at early stages. Published in npj Flexible Electronics, the work demonstrated a flexible sensor capable of mapping local magnetic and bioelectric signals when coupled to tumor models, offering a new modality for continuous tumor monitoring. The team validated sensor sensitivity and conformability in benchtop models and described integration with analytics for signal interpretation. Authors propose applications in preclinical drug testing and implantable monitoring systems that track tumor dynamics over time. Companies in flexible bioelectronics and implantable diagnostics could license sensor designs or integrate the arrays into companion‑device strategies for oncology trials.