Predictive text entry provides a fast way to enter text on phones and other small devices. Early work on predictive text entry highlighted that the reaction time for checking the screen dominates text entry times. Improving accuracy of predictions brings a downside: as prediction gets better, users will drop the slow operation of checking the screen and will thus miss prediction errors and system feedback/suggestions. In this note, we present an experiment into the use of vibration to alert the user when word completion is likely to aid them, using a dynamic approach based on their current typing speed, and when there are no dictionary matches to their entry. Results show significantly faster entry rates for users with vibration alerts, raising speeds from 20wpm to 23wpm once practiced.