The functioning of self-sustaining smart dust modules plays a vital role in the development of the smart electric grid. In this work, we first devise a flexible triple-junction III-V solar cell embedded inside a smart dust module suitable for outdoor applications. These flexible solar cells are demonstrated to have a bending radius of over 5 cm and exhibit a conversion efficiency of around 25% under air mass 1.5G (1 sun) conditions. Under normal incidence of sunlight at the same conditions, our cell with its small active area of 0.4 cm2 can generate around 10.1 mW of electrical power. This is sufficient to meet the direct current power consumption (∼5.4 mW) requirements of our dust module, which includes a temperature/moisture sensor, a 3-axis linear accelerometer, and a Bluetooth chip. In comparison to a silicon-based flexible solar cell, our demonstrated III-V solar cell is smaller, requiring approximately 40% of the area to produce the same electrical power output. Our dust module is controlled using a self-developed Android application installed on a smartphone and can sustain continuous-wave operation for data collection and wireless transmission even when the incident angle of the sunlight reaches 75°. Pulse-mode operation is still possible even in the case of nearly 90° illuminations (for example, at sunset). Overall, the measurement results for this flexible solar cell are promising, allowing for further reduction in the size of a self-sustaining smart dust module with improved reliability. These advantages could facilitate development of the next generation of energy saving smart electric grids.