Currently, there is a lack of stand-alone geo-monitoring systems for harsh environments that are easy to configure, deploy and manage, while at the same time adhering to science grade quality requirements. In a joint computer and geoscience project we have built and deployed a wireless sensor network for measuring permafrost related parameters. Using these high-precision data, geo-scientists will be able to calibrate their heat flux models in order to better predict the stability of steep rock slopes in the alps. In this paper we describe our system from a computer science and system point of view and report on some lessons learned, especially in the domain of sensor design, power-awareness and reliable data flow. Categories and Subject Descriptors C.2.1 [Computer-Communication Networks]: Network Architecture and Design; C.2.3 [Computer-Communication Networks]: Network Operations; J.2 [Physical Sciences and Engineering]: Earth and Atmospheric Sciences General Terms Design, Measurement...