Among the different challenges induced by Wearable Computing, is the one of IO devices. The choice of appropriate input device is driven by the user context and the availability of motor resources of the user. The substitution of one device by another with same functionalities is not sufficient. After the introduction of input devices classification, we show that it is necessary to introduce a user model for input devices considerations. A simple example based on motor resources of the user permit to illustrate our method. Copyright 2005 ACM.