Reicast is a Dreamcast emulator for Android that will run on phones, tablets and set-top devices such as the Ouya. Although its an Alpha it appears to run quite well on my 2 year old Galaxy Nexus phone. Sound works and games run at full speed with the ability to save. On my Galaxy Neuxs the games appear to have graphical glitches, however from looking at the screenshots on Google Play that's not the case for all devices. Recast can be downloaded free from the Google Play store: Download Reicast