Could LaTeX be used to take notes in class on 5'5 smart phone well? Is there some application or method to use LaTeX on phones?
If you're only interested in typing, then just use a text editor. If you want something a bit more, you can get vimtouch (I used to use it religiously).
It's advised, though, to use hacker's keyboard, b/c other keyboards won't have the backslash and such.
If you're really into it, and you're rooted, you can rule a full blown linux distro. More details can be given if you're interested (I'm on mobile now).