Twit2LJ is a service that runs on your phone. Once per day (at 4 AM by default), it takes all the tweets you posted during the previous 24 hours, and formats them into a Livejournal post. It also takes pictures that you linked to (from pic.twitter.com or flic.kr), and shows them in the Livejournal post.
To set up Twit2LJ, launch the app, enter your twitter username, livejournal username, and livejournal password. Then check the options you want. Finally, click "Post Daily Digest to LJ Now" to do a test post. The log at the bottom of the config screen will show any errors that are encountered (like a typoed username or password), or will say "Success!" when it has completed without error.
You phone must have a data connection at the appointed time for the automatic posting to work. If it doesn't, it will retry every 20 minutes.
To see Twit2LJ in action, visit colmmcsky.livejournal.com, where all the posts are generated from the twitter account @colmmcsky.
Twit2LJ is Open Source, licensed under the GPL 3. Source code, Wiki Documentation, and bug reporting can be found here: http://code.google.com/p/twit2lj/