The "TwitterPeek," made by New York-based Peek, costs US$100 with six months of service or US$200 for a lifetime service plan.

Peek, which also makes mobile devices strictly for e-mail or text messaging, called the TwitterPeek "the world's first dedicated Twitter mobile device."

"Because TwitterPeek is designed for Twitter, it provides a tweeting experience superior to any website or smartphone application," it said.

The device resembles a Blackberry smartphone with a full-color screen for viewing messages and a keyboard for typing them.

Twitter, which allows users to pepper one another with 140-character-or-less messages known as "tweets," has grown rapidly in popularity since it was launched in August 2006 and claims to have topped 50 million users.