I will update the first post with proper info now, but here are answers to all questions.
How finished is this, when will it be available, and how well does it run?
Obviously it's far from being finished, mostly because I started not long ago - things are going fine, no difficulties I don't know how to overcome so far.
Did you actually port DF to iOS or is it an iOS app that communicates to a remote server? You're talking about a protocol; what do you mean? And of course as Max™ said, is there any chance this could be adapted to other operating systems?
Yes, it's an iOS app communicating with a dfhack plugin (mostly in Lua). The protocol provides high-level access to all the actions and data (once finished) in the fortress mode. For example, 'give me an info on this building', 'give me a list of possible jobs for this workshop', 'add job at pos N from that list', 'allow a squad at position N to train' and so on (and of course map updates). Clients can have a UI modelled after the original DF interface/screen structure or something very different to make it more user-friendly and appropriate for the platform it's running on.
I have many small ideas to make better experience on mobile devices like accessing buildings from a list with 'favourites' function instead of going to it on the map, ability to rearrange items and search in all menus (designate, build, add job), grid view in these menus with icons only for faster access (that's why I have those icons with usual DF keys), description of all buildings/jobs/... accessible from corresponding menus (sort of mini dwarf fortress wiki built-in), generated portraits on unit info screen if you like, icons and sounds for various announcement types, ability to run unattended while the app is in background until something happens and send push notifications when something happens, and so on.
Now I just hope Toady won't have anything against all of this in general for some reason.
Wouldn't it be sloooooooooow as a crippled elf?
It's totally playable via 3G. Actually, depending on the server location - if it's on the other end of the world it probably won't be good, if it's your server at home then it's fine.
This is great. Maybe you could externalise the code that connects your interface to DF into a library?
That's the idea. Well, not a client library, because it's platform-dependent, but the protocol and server-side code.
Will you be able to put this on android? It's super-awesome, to whatever use it gets put, but I'd love it on my tablet.
iOS version alone is enough work for me for a long time (with all the ideas I have), and I'm an iOS developer, so I personally won't be doing other platforms, but others hopefully will.
it could probably be pretty useful for building the fabled multiplayer-df. Even if it isn't it I'm sure I could poach all sorts of bits and pieces for Webfort.
Unfortunately the more I work on this the more I think that a proper multiplayer won't be possible. DF uses too many global variables related to UI and current game state and there are some other complications that do not arise in single-player mode.