To the Speech at CMU page. Unlike GUI design, speech interface design is still in its infancy. As we gain more experience our understanding will improve. These guidelines have been found effective for interfaces that are part of desktop computers, this being what we are the most familiar with.
Wearable computers are an important class of such devices.
Since such devices lack GUIs, the interfaces begin to look less like traditional interfaces and begin to assume some of the characteristics of human interlocutors in their ability to maintain a communication channel with a human user. A short working paper on this topic is available. More information may be obtained from Alexander Rudnicky .