There's a reason that we're all still carrying physical keys around with us: they're simple, they're reliable, and while you might forget the key itself somewhere, you don't need to remember anything else besides how to put the key in a lock. A recently-spotted patent from Apple suggests that it's trying to make laptop chargers work the exact same way.
Apple's thinking here is that as the battery life of mobile devices improves to the point where we're getting reliable all-day use, people will start leaving their chargers at home. And if your charger stays in a safe place, you might as well use it to unlock your computer or cellphone or tablet or whatever else ends up with this technology in it. When your device isn't plugged in, it'll have a password like normal (you do use passwords, right?), but as soon as you attach a charger, the charger will be all "hey you're safe now," and the password protection will disable itself. As an added advantage, if you ever forget your password, you can just use this method to get into your computer and change it, kinda like having a spare key.
This concept potentially extends beyond chargers to any other hardware that your devices can connect to. Like your cellphone, for example. Or your home wireless router. Wouldn't it be handy if all of your gadgets would automatically unlock themselves whenever they knew they were safe and sound at your house? And then whenever they were outside, they'd switch back over to asking for your password again.
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The obvious downside here is that if anyone ever steals your laptop and your charger (or your cellphone or wireless router or whatever your laptop happens to be linked to), they'll have immediate access to all of your data. But, for people who carry their iWhatevers around with them everywhere, this should help protect you and your files from casual thievery.