At Chirp conference, Evan Williams announced that Twitter microblogging service network would be launching an Android application. It’s unclear whether Twitter will acquire an existing app, will partner with a developer or mobile device maker (as did with RIM for BlackBerry Twitter app), will it develop own app. Last week, Twitter acquired Tweetie, highly polished Twitter app for iPhone (now called Twitter for iPhone). And on Friday, Twitter announced that RIM’s new BlackBerry app would be an “official Twitter app” for the device. These announcements came after investor Fred Wilson wrote a post telling Twitter start-ups to stop filling holes in Twitter’s products and to instead look to launch killer apps that start entirely new businesses.