Tweetpkr is simplicity in viewing your Twitter stream. You enter your Twitter username and password and a bookmarklet is generated that works across all the browsers. You can even make ones for numerous accounts. When you click the bookmarklet from anywhere you are browsing, it opens a side panel that shows the Twitter stream for those you follow.
There is really no other function or integration right now and I had a hard time counting this as a client, but there were no rules that a client could not be read only.