Click Install to get iNDS, no jailbreak required on iOS devices for free.
iNDS is a port of the multi-platform Nintendo DS emulator to iOS. Currently, emulation is powered by the DeSmuME threaded ARM interpreter and runs at nearly full speed on the iPhone 5 and above. Due to the need to map the entire ROM into memory, older devices with only 256MB of RAM are not supported. These devices include the iPod touch 4, iPad 1, iPhone 3GS, and anything below those devices.