Epi Info™ is a suite of public health software tools for use by public health and medical professionals. The Companion for Android is a free, lightweight, and easy-to-use application that allows you to quickly and easily calculate sample sizes, collect data, and perform analysis using your smartphone or inexpensive tablet. This free app allows you to do all of this on your smartphone or tablet, and you don't need to have any specialized hardware or IT infrastructure to do so. In addition, the Companion for Android can be used to collect data for public health studies, and it can be used to respond to emergencies and other urgent medical situations. The app is ideal for use by public health and medical professionals in locations with limited IT infrastructure.