It would be easy if the email which receives your cell-phone emails is a POP account.
Let me know.

I've actually started on this in a half-arsed sort of way. I was making a dummy POP3 box at my domain that would be checked every five or ten minutes and all e-mail received would be parsed and piped out to LiveJournal. Basically, the e-mails would have to be formatted like this:

user xb95
password blah
text
The text of the entry goes here, and continues, until another text line is encountered.
text
[music this is my music]
[mood this is my mood]
[journal journal_to_post_in]

Lines in []'s are optional, of course. Not sure if this is very useful to anybody, but... :)

You shouldn't need to handle raw sockets, that's only really if you're making your own protocol. For existing protocols, there are libraries/modules to deal with the socket-level operations.

I pondered making almost the exact script in perl, running as a daemon on my linux box. Basically it just checked a POP account every 60-seconds (say, lj-entry@domain) and parsed the body of the message for username, password, subject, meta-data, and body of message and sent an email back with the status of the post.

You can do this with about 5 lines in procmail and 5 lines of changes to the Perl LJ client...

Though getting something on the LJ server would be a bit more complicated.

Yeah, I did this for my personal use on my web site... just for this purpose.

lj.username.password@bradland.com

Pretty ghetto, but works just fine.