In fact, you could run a remote Emacs and edit LaTeX with it, using the excellent AUCTeX package. Of course, that means you need to have a network connection plus a server you can ssh into.

You'd also need to see the layout graphically? (Also, I assume every LaTeX user has a few computers to use as servers..)

Edit: Clarity.

I don't know about running Emacs over ssh on an iPad, but locally using the X front-end (e.g. not in a terminal), Emacs can display PDFs.

It might get tricky though to issue the latex command on the remote server from the Emacs that runs locally?!

I've never tried using auctex remotely, but in general if you have a file open in Tramp, you can also run arbitrary shell commands with M-! and M-& remotely, as well as opening shell buffers that let you run commands remotely as normal.

Yeah, that's right... You could scp the .pdf back to the iPad, but that's a bit cumbersome. Oh, well, unless you give Emacs advice to do that for you after each latex command...