Why settle for a cell phone that just rings when you can be alerted to a call by the whistling chorus of Jay-Z’s ”Big Pimpin”’? YourMobile.com has been offering customized rings for nearly four months, and already 2.5 million tone seekers (mostly guys ages 15 to 25) around the world have logged on. Top tones change daily, but include hits from Cher, Eminem, Limp Bizkit, and Moby. The appeal? ”Most of the time, we’re embarrassed if our phone rings,” says Mobile CEO Anthony Stonefield. ”But if there’s an interesting tone, you say, ‘Let it ring. Let everyone thoroughly soak in how cool I am!”’ Or conversely, what a geek you truly are.