This paper describes the design, fabrication and initial characterisation of a MEMS-based environmental monitoring system. Intended for use with miniaturised Wireless Sensor Network (WSN) motes, the die measures 3 x 3 mm and incorporates humidity, temperature, corrosion, gas and gas flow velocity sensors on a single substrate. Fabricated using a combination of surface and bulk micromachining technologies, the sensor system is designed to replace discrete components on WSN module boards, thereby minimising space consumption and enabling smaller, cheaper wireless motes. Sensors have been characterised over a wide range of environmental conditions. An analysis of the effects of changes in environmental parameters other than the measurand of interest on the performance of the temperature and humidity sensors has been carried out, and corrections applied where necessary. A variety of corrosion monitors have been demonstrated. A gas flow velocity sensor, based on forced convective heat transfer and which has been thermally isolated from the silicon substrate in order to reduce power consumption and improve sensitivity at low flow-rates, has also been presented. The paper also outlines the design of the next generation sensing platform using the novel 10 mm wireless cube developed at Tyndall. (C) 2009 Elsevier Ltd. All rights reserved..