Wireless sensor networks are collections of autonomous devices with computational, sensing and wireless communication capabilities. Research in this area has been growing in the past few years given the wide range of applications that can benefit from such a technology. This paper describes a customisable sensor–actuator interface board for use in a highly modular and miniaturised wireless platform. The interface board has a 25 mm × 25 mm form factor and allows any combination of eight different sensors and actuators to be connected to the Tyndall25 Mote that contains the computational/RF components. It can also be used in conjunction with various other developed layers in the 25 mm system for specific applications. One intended application area of this hardware is in the horticultural/agricultural industry.