User-defined foot-gesture is a promising approach to interacting with mobile devices when both hands are occupied. In this research, we first present a survey to identify how often interacting with mobile devices is needed when both hands are busy and how many tasks people commonly would like to do on the devices in such situations. We then present a study to compare a traditional approach with foot-gesture interaction in a simulated hands-occupied scenario. Results show that foot-gesture saved over 70% of the time compared with the traditional approach and was perceived more useful and satisfying.