This dissertation describes three systems to help people better understand and debug the behavior of embedded electronic systems. The underlying shared principles across these projects are automatic instrumentation, visualization, and checking. The first, Toastboard, is a system for electronics prototyping that combines an instrumented breadboard with a web-based GUI and checks for common circuit construction mistakes. Bifröst extends this idea to systems that involve both code and circuits by simultaneously instrumenting a user's embedded code and microcontroller pins. Bifröst focuses on tricky to debug errors that can occur at the boundary between software and hardware. Finally, Wifröst addresses difficulties encountered when connecting embedded devices to the Internet. Wifröst instruments and collects data from a user's code as well as network infrastructure in order to guide users to the underlying reasons for and solutions to failures. These systems were evaluated through debugging tasks and user feedback. Taken together, these systems envision a future in which non-experts have a much greater understanding of the behavior of embedded computing devices in order to more effectively build, combine, repair, and audit their functionality.