UPDATE #2: More competition has come onto the market. Check out the Snake ~ Chicago Snake lock solution. It looks a lot less scary (in terms of potential scratching) than the others, like macBracket. It's $20 and available from Amazon, where several pictures of how it works are shown. You can also find it at its home page.
UPDATE #1: It turns out this is not the only bracket available. As reviewed by MacGirl.net, there used to be a bracket sold on an eBay store that slid up through the MacBook Air. Unfortunately, not only was the locking portion in front of the screen, but it could slide around and scratch the device. Then came the macBracket out of Germany. The macBracket is pretty slick and looks like it is relatively gentle on the MacBook Air. It's a little pricey, but it's not like there's a lot of competition right now.I was surprised to hear that the MacBook Air has no Kensington lock slot. It's too small. Apparently, some of the PC ultrabooks also have this problem. Tablets have this problem, but it's easy to take tablets and phones with you... It's a little harder to carry the MacBook Air everywhere.
So if you need a good solution right now, check out the macBracket. Just make sure to order the correct version for your MacBook Air; they have support for new MacBook Airs (MBA). That new MBA bracket will be shipping soon (at the time of this posting), but it's available for order on their website.
There are a ton of alarm solutions (like what you'd expect to see in a BestBuy) that rely on USB connectivity or adhesion or something similar. Those aren't really ideal. A lock is what is really needed. I've seen two locking solutions available for purchase, and both of them are a bit ugly.
- The first, from MacLocks.com is a protective case which attaches to the bottom of the MacBook Air with screws. The protective case includes a Kensington lock slot, and so your MacBook Air can be locked down so long as the potential thief doesn't carry around the right screw driver (some sort of security star head or something like that). I suppose they could have used those non-removable screws that only support a driver in the clockwise direction (like in many bathroom stalls), but then you'd be out of luck if you ever wanted to get the case off of your MacBook Air.
- The second, from JKLocks.com, has a few variations. I saw version RL108 on YouTube, but there are other versions on the company website. It uses 3M command strips to attach a Kensington lock slot to the back of the laptop. When the lock is connected, it covers the ends of the command strips so they cannot be removed. Of course, if you ever try to remove the command strips, you have to be very careful the metal base of the Kensington lock slot doesn't go scratching across the top of the laptop (!!).
That's genius! It is just an eared sickle that slides through the hole between the screen and the keyboard; the hinges and lock keep it from sliding out! Unfortunately, the inventor cannot find any partners willing to fabricate it in large quantities and market it. Sure, it would need to be built so it could be tough while not scratching the device (and would need to be fabricated for relatively cheap). However, I think those challenges are not insurmountable.
So do you have some dough laying around and want to market a great idea? If so, contact the inventor and start selling these things! Get them out before there are a lot of ultrabooks on the market -- I'm guessing there will be a demand for this little portable toy!
Meanwhile, you could probably fabricate something similar yourself (e.g., with some coated aircraft cable thin enough to slide through the MacBook Air). It might be hard to make it compatible with a Kensington lock without some fabrication, but you could surely make it compatible with a padlock.