hell yeah. you can do your whole friends list at once.
when they first offered lj phone posts, i wasnt a paid member so i made my own.
all i had to do was send a voice memo on my phone to an email address. they show up as wav files. there was a cronjob set for every 30 minutes (or something?) to pull wav files from the spool and convert em to mp3s and drop em in the public_html. the files were named with a prefix of the date and time so as not to overwrite old ones. then the script used an automated LJ posting tool to paste my "PHTs improvised phone post code" (even used the same icon as LJ does) into a new post with link to the mp3 and the date and time.
it was hottttt. i barely ever used it though. then i got a paid account.