What does Sarah need from us on the go? That's what drives Hearst as it adds bells and whistles to mobile sites that are companion to magazine brands such as Cosmopolitan, Redbook and Marie Claire.

The typical reader for Cosmo's print edition, for example, is a woman in her twenties, which is also the target demographic for the Cosmo mobile site at http://m.cosmopolitan.com. Hearst likes to call the composite of this reader Sarah.

"[The mobile sites] are keeping her company at different times in the day," said Sophia Stuart, director of mobile at Hearst Magazines Digital Media, New York. "There's a sense of mobile becoming a companion."

What are the gaps in the Cosmo Mobile reader's day? It's those gaps that the site is looking to fill with engaging content.

For example, the first thing the Cosmo mobile reader does is check the weather and horoscope.

The Cosmo mobile site now boasts new features to keep the reader entertained. There's "You - even better," a section that's all about the Cosmo woman.

Another addition is the "Dude Decoder" to help women understand male body language, which they claim is a mystery to them.

Marie Claire's mobile site added a new blog called "Dating Diaries." The title says it all.

For its part, Redbook's mobile site runs the "Infertility Diaries," following the trials and tribulations of two editors who are trying to get pregnant. The site also hosts a blog called "Diary of E."

This week, the Redbook mobile site will introduce "Hot & Bothered," a dating blog.

"The blogs are a huge feature for us," Ms. Stuart said.

The nine Hearst mobile sites are powered by Crisp Wireless, New York.

Meanwhile, the Cosmo mobile site recently won a Webby award, beating Disney, NBC and Bravo in the mobile entertainment category.

Hearst has tailored its mobile sites keeping in mind the needs of today's young woman.

"She wants information, entertainment, comfort, ideas," Ms. Stuart said. "Sometimes she wants companionship. That's why she'll read blogs. Sometimes she'll want deep information on products.

"We want to be with her wherever she is," she said.