There are only some inferior apps based on desmume, better desmume alternatives in Retroarch and a melonds core which is still "young" and inferior to the main PC emulator.
For example one major feature we miss on Android is multiplayer and just imagine how awesome it would be to have it working when everyone and their dog has a phone and internet connection nowadays (even if it's your neighbors WiFi or the WiFi of a public place

One less requested feature is using and be able to modify our own firmware files like in desmume and melonds.