I've been playing around with the SMS options on Fastmail.FM.
One problem I had was that long messages forwarded by SMS seemed to get truncated long before 160 characters were reached, so I tried out the various options.
Finally, I found a combination that would apparently forward the first 158 characters of the subject, and that was easily modified into a custom command to forward the first 158 characters of the body. (Though my first attempt sent only the word "$body$" since I had misremembered the magic variable "$text$".) I've no idea what happens to the last two characters.
So now, apparently that plays nicely with LiveJournal's text message facility -- when set up with a provider of "other", it'll accept a maximum of 100 characters, minus the length of the sender's username. So when I tried it myself, I had 97 characters to play with.
The message itself started with "(f:pne)", which has four characters in addition to the username, but eh. Even 104 is less than 158, so text messages sent through the LiveJournal interface should now reach me completely. (Only those on my friends list can use the feature to send me text messages, though, since each message forwarded that way costs me a bit of money on the Fastmail.FM front.)