Smart agriculture systems, which integrate sensors and data analysis into agricultural production processes, are increasingly proving an effective solution for reducing food production waste, yield production increase, and product quality improvement. In this context, this paper deals with a wireless sensors platform for humidity, temperature, and light detection that has the peculiarity to be self-powered and battery-free. The main advantage of the proposed solution is the elimination of maintenance interventions due to battery replacement. Therefore, the availability of install-and-forget sensors allows an easy diffusion for a capillary detection of plant health and growth parameters throughout the cultivated area. The device platform implements off-the-shelf components on a printed circuit board (PCB) with the size of 2 x 2 cm2 and the thickness of 0.45 cm. The sensor platform can harvest energy and supply the sensors with light intensity as low as 300 lux and communicate with Bluetooth Low Energy communication. Experimental measurements carried out in the rural context of the rows of a vineyard show the system functionality with a reliable communication distance, between the sensor platform and a remote Base Station, within a radius of 160 m.