The global rise of text entry modalities that are not desktop QWERTY keyboards—and therefore exhibit significant uncertainty in input actions—has created enormous opportunities for language technology to improve the quality and efficiency of these tools. In addition to the near-total ubiquity of smart phone touchscreen technologies, specialized communication tools for people with disabilities have exhibited a similar growth in research and adoption. While language technology is known to be a crucial feature in these text entry tools, its specific application is not always deeply studied. In this dissertation, I will explicitly examine the constraints and opportunities afforded by incrementality as they apply to language technology for text entry. In particular, I will explore user-directed text revision and error correction in these tools.