I've had the pleasure of playing around with Twitterlerts for a while now, and I can say it is a very cool app for Twitter "power users". Twitterlerts lets you easily search Twitter right from your device, and you can save custom searches and even set alerts. Essentially a Twitter search app for BlackBerry, you can also sign in with your Twitter account and use Twitterlerts as a slimmed down client to send updates, replies and follow other users.
Twitterlerts is the Twitter client that makes its easy to stay on top of the subjects that really matter to you - and reveal a world of ideas, comments and opinion on what is important in your life - your company, your products, your competitors, sports team or hobbies.
Sure there are search functions in other BlackBerry Twitter clients as well, but if you need to stay on top of things on Twitter, maybe you'll want to make life easier and give Twitterlerts as shot. It is available until August 31st for $4.99 and is regularly $7.99.