As an emerging technology that combines mobile and wearable markets, smartwatches are finding their place on consumers’ daily lives. They allow tasks that used to be performed only by smartphones and tracking devices. Despite the increasing interest on them, a task that is still not fully covered by these devices is text entry, mainly due to their reduced screen size. Researchers have been working hard on solutions for this issue in the past years, and a number of methods for interactive text entry with smartphones now exist. The aim of this paper is to present a systematic review on these methods, showing what has been developed and what is the performance of the current state of art of the technology. The review focused on four databases. After applying a large selection criterion, it resulted in twenty six approaches, which helped to answer questions that grounded this work. We hope to deliver a rich and useful foundation about methods, results, challenges and opportunities and to support new research on smartwatches.