Curious what cellphones your favorite celebrities use? Take a look at their Twitter feeds. Oct. 19 was a good day for Heidi Montag--and for AT&T. That was the day the wireless operator gave the reality show actress and aspiring singer a BlackBerry Bold in a striking new color--white. Montag posted a photo of the phone on her Twitter account with the caption, "I LOVE it!! My new phone!" Within minutes, dozens of Montag's 690,000 Twitter followers clicked on the photo and expressed their approval, calling the phone amazing, gorgeous and stylish. One noted, "AT&T always has the best phones," while another joked, "I think I know what I'm getting when my T-Mobile contract is up!" To a carrier like AT&T--and BlackBerry maker Research In Motion--that kind of publicity is golden. To elicit it, they "gift" or "seed" products for free to celebrities at concerts and award shows or via mail or messenger service. The practice isn't new, but the rise of micro-blogging services like Twitter make it easier than ever for companies and fans to keep tabs on the cellphones that celebrities use. Previously, consumers had to rely on in-person sightings, paparazzi photos and celebrity interviews for clues. On Twitter, tracking mobile preferences can be as simple as watching for a tweet (or message) like Montag's that refers to a particular phone. For celebrities that are less effusive (or exhibitionist) than Montag, a quick read of their Twitter status line usually offers insight. That's because Twitter cites, by name, the method or software used to post messages. Those programs, in turn, often reveal what kind of phone--or what kind of mobile operating system--sent the update. Consider John Mayer. The singer, who updates his Twitter account multiple times a day, has been utilizing a program called Twittelator for many of his tweets. The software was created specifically for the iPhone, making it easy to deduce that Mayer uses an iPhone, at least part of the time. Other celebrities leave similar clues. Lance Armstrong, Katy Perry and Jessica Simpson employ UberTwitter to post messages to their Twitter accounts. The service works only on BlackBerrys, pegging them as BlackBerry users. Mariah Carey and Oprah Winfrey mostly update from the Web, but occasionally use TwitterBerry--another BlackBerry Twitter program. Lady Gaga uses both UberTwitter and TwitterBerry to send updates about her concert tour, new videos and fashion obsessions to nearly 1.8 million Twitter followers. (One recent tweet: "In studio writing music, already used up a whole can of hairspray. Feels like home...") Twitter followers of Chad Ochocinco, the tech-savvy Cincinnati Bengals wide receiver, can see that he updates via a service called Motoblur. The program is part of Motorola's social networking software for its Google Android smart phones. Since it's only available on one phone right now, it's clear that Chad Ochocinco uses a Motorola Cliq. Promoting Motoblur is to Ochocinco's advantage, as Motorola uses the technology to distribute his social media news service--Ocho Cinco News Network--to fans' phones. Indeed, some of these celebrity preferences stem, in part, from business deals. Consumers likely associate Whoopi Goldberg with the T-Mobile myTouch 3G. That's no accident: T-Mobile hired Goldberg, biker Jesse James and Los Angeles Lakers coach Phil Jackson to star in TV and print ads for the phone. LG tapped model and TV host Heidi Klum, actress Hayden Panettiere, singer Ciara and fashion designer Christian Siriano to promote its handsets in 2009. Samsung asked actress Audrina Patridge to host an event for its Mondi, a handheld device that runs on a fast type of mobile broadband called WiMax. Other companies focus more on distributing phones to select celebrities. Nokia sent one of its new phones, the Twist, to several young actors including Taylor Lautner and Jonah Hill. RIM may boast plenty of famous users already, but it still gives out free BlackBerrys, most recently during a U2 concert tour that it sponsored. In the rush to get new phones into celebrity hands, a relatively small company--Palm--appears to have done the most outreach. In February, just a few weeks after unveiling its Pre handset, the smart phone maker gave phones to nominees at the IFC's Independent Spirit Awards. In September, Palm distributed more Pre's at the Emmy Awards gift lounge and showed off a slimmer smart phone called Pixi at New York Fashion Week. It also hosted a launch party in June and gifted phones at a Major League Baseball All Star event in July. All told, at least 30 celebrities, including actors Blake Lively, William Shatner and Tracy Morgan, received Pre's or Pixi's this year, according to Palm. Many posed for pictures, which Palm then posted on its blog and documented on its corporate Twitter feed. (Sample tweet: "William Shatner and wife already use Pre. She said: 'I love it so much I want to name it.'") When it comes to celebrities and cellphones, the details usually end up on Twitter. Sources: Forbes