The main reason I backed the FunKey was its GBA capabilities, but I imagine that this varies greatly for each person, depending on which games interest them most. The currently announced systems that the FunKey can emulate are the NES, SNES, GameBoy, GBC, GBA, Sega Master System, Sega Genesis, Sega Game Gear, PS1, Atari Lynx, WonderSwan, and the Neo Geo Pocket, along with upcoming MAME capability being mentioned in the comments. However, this made me wonder exactly what else the FunKey could do. Assuming that the N64 and DS are beyond the current capabilities of the FunKey, what other systems could the FunKey possibly emulate? Personally, I would be interested in a way to play DOS games, preferably without needing to type into the command prompt. And while the Kickstarter campaign mentions how it intentionally doesn't come with shovelware mp3 and text readers as many cheap knockoff emulation systems do, having the option to download additional apps from a page on the website would be cool. If using headphones through the Micro-USB port becomes a possibility, using the FunKey as a tiny MP3 player would be cool as well!
Also, while the device is of course not the most practical for it, an MP4 player would be a fun addition; since the GBA can play videos if you jump through several hoops of conversions and downgrading, I imagine that despite the resolution not going to be much better, running videos outside of an emulator might improve the FPS and bitrate videos could be loaded at compared to the GBA.