Researchers at University of Duisburg-Essen and Nokia Research published a paper evaluating capacitive touch input on clothes.After the evaluation, they proposed guidelines to successfully design wearable controllers.
First, it is a very tough problem to find a design and layout of button inputs that match the ideas of a majority of users. This issue can be softened when having a clear mapping from appearance to function. This leads to the second recommendation that finding a specific control must be made as simple and quick as possible. This requires well designed visible as well as haptic cues. We also provide hints as to the location on the body that is preferred by people. Thirdly we stress that it is most important to have the controls placed in a way that one-handed interaction is easily possible. The fourth main guideline is that the system needs to ensure that feedback for the actions needs to be without delays; otherwise users can not be sure about whether or not their input had been registered which then can lead to frustration or accidental multiple button presses.