In March of 2007, former British Prime Minister Tony Blair's crime task force suggested that iPods should come with fingerprint readers that would lock out anyone who wasn't the owner. Presumably the way it would work is that an iPod would come tabula rasa and "imprint" on the first finger that touched it. Thereafter, if any other finger attempted access, the machine would lock up until it saw its master's digit once again. Aware of this situation, a thief wouldn't bother stealing the iPod in the first place. (Either that or he'd steal your digit, too.) Problem (more or less) solved. The same technique could be applied to cell phones, PCs, Playstation Portables and other electronica.
A fingerprint iPod would be rather like a tattoo or a pacemaker: You can admire mine but if you want one, you have to get your own. I believe economists would say that they are "inalienable" property—as opposed to "alienable" property (like bananas or the flu), which can be transferred.
The secure iPod is part of a larger notion that crime can be "designed out" of products by making them intrinsically secure, an elegant idea. Apparently the task force's report doesn't put forward any examples other than the iPod, which is a shame...but since it's our job to speculate...
Biometrics are the obvious (but not very interesting) way to go. If a fingerprint or retinal scan is required to activate a device, then thieves will apparently be stymied (ignoring the digit theft observation above). An expensive item (such as a car) may require better biometrics since thieves will have a greater motivation to bypass its security.
There is another, more provocative option, however: absorption. It's hard to steal a Bluetooth headset when it's lodged in your ear canal. And cell phones: The display and keypad could conceivably be absorbed into a forearm (or some forearms: Forearms that played football in university, let's say, rather than forearms like mine that were on the dance committee). This is of interest mainly in countries where carriers don't subsidize the cost of phones, so a $500 phone really is worth $500 and hence is worth stealing.
Note that there's a balance to be struck, here. The more expensive an item, the "deeper" into your person it must be absorbed. The last thing you want is for a thief to do a mess/benefit analysis and decide that your valuables are worth the trouble. Keep your retirement savings in the form of small gold ingots securely stashed in your abdomen? Be afraid.