DeSmuME is a Nintendo DS emulator for Windows, Linux, Mac OS X, and Android. It allows users to play their favorite Nintendo DS games on their computer or mobile device. It features a full-screen mode, dual-screen support, joystick support, configurable hotkeys, and supports save states, cheats, and more. It also features support for the Illusory Wall, a game-style that displays the top and bottom screens of a Nintendo DS game simultaneously. DeSmuME is an open-source project, and is constantly updated with new features, bug fixes, and performance improvements.
It is the best DS emulator for Android. Well worth the price. It has all the features you could ask for, except the multiplayer / link function.