RSVPs:  Emmy Rossum, Amy Smart, Paris Hilton...
When:  Aug. 8
Where:  Sunset Tower Hotel

It has only been two months since my last cell phone party, but I have a feeling tonight's Helio Summer Event is going to be a good one. The cell company is using the Ocean—their newest device, which features a camera, video and GPS—as a medium for spreading the word about Heal the Bay Coastal Cleanup Day, held annually on the third Saturday of September. And it looks like the word is getting out: When I arrive at the Sunset Tower Hotel, beach babe Jennifer Aniston smiles at me before walking into the lobby. Looks like this party is going to be better than I thought.

Going Green, Blue and Girlie
The patio of the hotel is filled with celebs like Erika Christensen, Clifton Collins Jr. and the recently engaged Elisabeth Rohm. "I live in Venice," the former Law & Order ADA says, "so it’s my great incentive to actually make sure the oceans are taken care of. It's my backyard." Okay...but would she be as green if she didn't own oceanfront property?

The beaming bride-to-be much prefers talking about her new state of womanliness. "I feel much more feminine," Rohm says about her upcoming nuptials to entrepreneur Ron Wooster. “After all those cops and lawyers I played, I actually now feel like a girl." She's dressing the part, too, looking completely angelic tonight in a satin sheath.

Classy and Trashy
But the true girlie-girl of the night is Emmy Rossum, who's hosting the event along with Amy Smart. "I try to always be a lady," the 20-year-old says with such poise you’d think you were talking to Audrey Hepburn. "You don’t have to show too much to still be sexy."

Bai Ling, are you paying attention? As Emmy and I are chatting about fashion, Bai strolls up the red carpet and another journalist inquires about the designer of her shoes. The actress bends down to take a look at the label and—bam! There's a clear shot of her undies. But at least she's wearing some—and not pulling a Britney!

Kudos to Emmy for supporting tonight's admirable cause, but truth be told, she's multitasking at this party: Scattered on a nearby cocktail table are a bunch of CDs sporting her face on the cover. "It's very personal and very kind of baring of myself," Emmy says of her new Inside Out album, which drops in October. "It’s the first time I get to really express myself and not have to play a character." Considering she put her acting career on hold for a year to focus on music, the album better be good. Luckily, her sample songs already made it to number three on the iTunes pop chart, so things are looking promising.

Lights, Camera, Smoke
Amy, meet Emmy. Emmy, meet Amy. The cohostesses are asked to pose for pictures with Helio CEO Sky Dayton. "Nice to meet you," Amy says as she shakes Emmy's hand. Funny, when I cohost a party, it's with a good pal—but this is Hollywood biz, babies.

Speaking of Hollywood, where is that megastar Aniston? I haven't seen her since our close encounter outside. On the other end of the starry spectrum, I do see Rumer Willis out on the patio, chatting with Smart and having a smoke. "We have to be wearing skimpy outfits," I overhear Rumer tell Smart of the Anna Faris project she’s filming. "I haven't eaten all day." Bruce and Demi’s rapidly shrinking daughter forgoes the fried crab fingers, risotto balls and coconut shrimp, but she can’t turn down a chocolate-chip cookie. "This is going to be bad," she says, taking a bite.

Hey Rumer, if it's hotness you're after, sleep works wonders: The 19-year-old tells me she's been up since 4:30 a.m. and has to take a rain check for an interview because she's "so tired." If you're so tired, why not head home? 

The New Party Girl
Whatev. I'd rather talk to Paris Hilton, who's been looking spectacular these days. The heiress arrives at her usual hour-before-the-party-ends time in a sparkly BCBG dress, silver Fendi bag and a fresh face. "I did my makeup in, like, 10 minutes," she tells me. Well, it worked!

Ever since her jail stint, Paris has been acting more and more mellow at every bash. Could it be she's finally opened the professional chapter of her life? (Great for you, Miss P—but you're making my job waaay harder.) "There’s so much work going on, so many projects," she says of her upcoming clothing line, which launches at Kitson next week, and her future movie, Repo! The Genetic Opera. So, why is she out partying tonight?

"We can really make a difference if we all just get together and stop treating the ocean like a garbage can," she says. "When I have children and grandchildren, I want them to be able to enjoy the ocean, like I do, living in Malibu." First Nicole has a baby on board, and now Paris is talking tots? Maybe in 2025 we’ll see a new set of Hilton-Richie BFFs on Simple Life. Now there’s a scary thought.

An Aniston Hideaway
The party is winding down, but Rumer's still going strong, smoking and chatting with pals, like Six Feet Under's Freddy Rodriguez. Take a tip from Lindsay, li'l Willis: Nonstop partying is not a good thing.

Since I never did see Aniston again, I've decided it's time to call it a night. While waiting for the valet, I discover my favorite Friends star had pulled a fast one and cut into the Tower Bar restaurant for dinner. A party guest tells me Ms. Aniston started getting annoyed with the paparazzi craze surrounding her fave hang, Il Sole, and has been spotted at this quieter West Hollywood spot a bunch of times recently. Oops! I just spilled the beans. The Tower Bar probably won’t be so serene anymore. Sorry, Jen!