It’s a mobile world now. The PC and Mac no longer dominate the computing landscape. New handheld devices offer some stiff competition.

Computer maker Acer, for instance, is betting that people want smaller PCs in their homes that are easily connected to their smart phones. The company announced plans to release a slimmed-down PC and companion smart phone later this year.

It’s too early to tell if this fad will catch on. After all, the people who love their mobile-computing smart phones (re: me) also tend to enjoy the power of their home computers. Still, Acer’s play offers a unique alternative for computing.

Of course, with so much information finding its way onto mobile devices, security has become a big issue. If people are carrying around sensitive, personal information, one misstep could open up their lives to a host of scams.

To combat this, Japan’s NTT DoCoMo, the leader in mobile-computing applications and businesses, recently released a new phone in Asia that can recognize its owner:

The P903i from NTT DoCoMo, Japan’s top mobile carrier, comes with a small black card about the size of a movie-ticket stub. The card works as a security key by connecting wirelessly with the cell phone.

If an owner keeps the card in a bag or pocket, the phone recognizes when the card moves too far away and locks automatically to prevent someone from making a call. The user can choose to have the phone lock when it is 26 feet, 66 feet or 130 feet away.

The phone also comes with a handy GPS locator, allowing owners to track their mobile device.

Other Wireless Tidbits:

The mobile market may soon reach a critical mass with mainstream users, but it’s safe to say the teen market is already there. In a move that is sure to rankle educators, rapper P-Diddy and Los Angeles radio station XMOR-FM teamed up to offer local high schools the opportunity to have Diddy perform on site. The winning school sent 34,000 messages featuring the word “Diddy.”

Boston University is offering a class on mobile movie production, with students shooting short movies using only the cameras on mobile phones.