We present uncooled millimeter-wave (mm-wave) and sub-terahertz (THz) detection based on the sensitivity of field-induced insulator-to-metal transition (IMT) threshold voltage in Vanadium dioxide (VO2). We exploit the characteristics of reversible IMT in VO2 thin film devices, and demonstrate actuation of biased VO2 two-terminal switches encapsulated in a pair of coupled antennas on a Si/SiO2 substrate. We also study the behavior of VO2 switches interrupting coplanar waveguide (CPW)s for broadband measurement purposes. Finally, we propose an electromagnetic-wave-sensitive voltage-controlled spike generator based on a VO2 switch in an astable circuit. The fabricated sensors show record figures of merit, e.g. responsivities of 66.3 kHz/mW with a low noise equivalent power (NEP) of 20 nW at room temperature, for a footprint of 2.5 × 10-5 mm2. Our solution gives 3 times better responsivity with only 1/10 footprint of the state of the art which can be scaled down to few hundreds of nanometers. The responsivity in static measurements is 76 kV/W in the same circumstances. Our results highlight the capability of VO2 phase transition for building electromagnetic power sensors triggerable by low energy photons. Our experiments prove the concept within mm-wave ranges (40-220 GHz), while frequency scaling near-THz is feasible in similar design.