In many Ubicomp scenarios tiny wireless embedded sensor devices are used, and devices often collaborate to accomplish a common goal. This paper presents a group formation method designed for collaboration of devices. The paper analysis requirements for typical application scenarios, and then presents the general concept of the group formation process. The proposed formation method is a variant of an auction-based algorithm. The algorithm works fully distributed and is based on individual, private believes of the devices in the auctioneered item - e.g. a sensor value. The paper introduces the algorithm and analyses its effects analytically and in simulation. We show, that fully distributed operation, high robustness in the case of network failures and extreme low resource (energy) consumption can be obtained. We introduce an application case and present results from a real-world implementation.