User Interface Design Book for Electronic Devices?

ikeleib asks: "I'm in the process of developing a HVAC control system. The problem with most programmable thermostats and just about every other electronic devices is that they are hard to use. I've been trying to find a book on user interface design for electronic devices. All the books I've seen on interface design seem to focus on GUI's. Does anyone know of good books (or websites) on interface design for electronics? I'm talking about buttons and tiny screens, not web pages and dialog boxes. I've only been able to find one book (for $104)."