Have your MacBook lock itself when you get up to order coffee.

I work out of coffee shops all the time. It would be nice if my MacBook would just know when I stand up to go to the bathroom or order coffee - I don't need people mousing over to my bank website or iChat window when I turn my back on my computer, ya know? But it's not just that; I would love it if the minute I sat down, my Mac would just know I'm back and unlock itself.

Done and done, with Airlock. You install a preference pane and in 5 seconds it pairs with your iPhone via Bluetooth. You walk away, your Mac locks. You walk back, it unlocks. Not bad for $7.77.

[UPDATE: $7.77 gets you one license, but it's good for up to THREE Macs!]

It lets you set the radius of the lock/unlock boundary, and it lets you set the duration of time between each scan it makes to determine the proximity of your phone, and it even lets you assign any number of other tasks to have occur when you leave or return to your Mac (you can have your Mac say "goodbye" when you leave and "welcome back" when you return, etc.).

In my tests I had to set the range really tight and the responsiveness all the way up for it to behave in a way that could be useful. I also anticipate that running Bluetooth all day could drain a person's battery pretty fast - on both the MacBook and the iPhone or iPod Touch. But hey, I mooch off the cafe's electricity, so who cares? When I need to run Bluetooth, I have access to an outlet. No problem for me.

There is room for improvement, however. I would love a menu item that would enable me to turn Airlock on and off. I would love the general stability and responsiveness to improve (maybe Bluetooth isn't the ideal protocol to use? Have you tried the infrared sensor?). With a little imagination, one can begin thinking of other features that would be useful (not to mention a little more support on the website - a knowledge base or forum or something). I also wonder if this same technology could somehow work on a Bluetooth-enabled USB drive or other device that could function as a proximity key to my Mac. I'm sure it's in the works.

Now all I need is to get Network Location to automatically turn Bluetooth and Airlock on when I go to a cafe and off when I leave. That will be one of my next indulgences.