A free app for Android, by Electric French Fries.

The Human-to-Cat Translator is a free application for the Android platform that translates between the human voice and the sounds that cats make. The application is designed for entertainment purposes and does not provide true translation functionality. It is a tool that can be used to play with cats and make them do funny and entertaining things. It includes a 16-meow soundboard for instant access to common cat calls.

This includes a large collection of different sounds, and you can choose between different voices. It is very easy to use and can be used with your phone or tablet.