The official Twitter for BlackBerry app isn't too bad.
You can get it to buzz your phone any time someone on your following list posts a tweet. It has great support for searching hashtags and for clicking links to other users. It also previews images users post to their twitter. Your bold is perfect for it.
If you need help downloading it, I believe if you choose "Download through BlackBerry Browser", you can type in the email address your blackberry is tied to and it will send a convenient link to download it.