Diversity embedded codes are high-rate space-time codes that have a high-diversity code embedded within them. They allow a form of communication where the high-rate code opportunistically takes advantage of good channel realizations while the embedded high-diversity code provides guarantees that at least part of the information is received reliably. Over the past few years, code designs and fundamental limits of performance for such codes have been developed. In this paper, we review these ideas by giving the developments in a unified framework. In particular, we present both the coding technique as well as information-theoretic bounds in the context of Intersymbol Interference (ISI) channels. We investigate the systems implications of diversity embedded codes by examining value to network utility maximization, unequal error protection for wireless transmission, rate opportunism and packet delay optimization.