Commodity hardware enables a range of cost-effective ubiquitous computing research, but innovative custom hardware can drive compelling new user experiences. One of the dreams of ubiquitous computing is an ecology of heterogeneous computer systems, built into the environment around us and acting in concert to make our lives easier and more fun. Fundamental to this vision is a movement away from the desktop computing metaphor, in which a single user interacts very intentionally via a display, keyboard, and mouse. Instead, many researchers imagine computers with very different forms that support rich and varied means of interaction.