Home Zone is an application that makes your Mac automagically do stuff based on whatever wireless devices it detects around it. I personally use Home Zone by configuring my Mac to automatically fire up its screensaver and locking itself whenver I leave the vicinity of my computer. I also configure my Mac's volume to mute when I (and my cellphone) leave its side. Home Zone can also be configured to configure your Mac to whatever wi-fi access point it detects. So as you go to the office, it can automatically adapt itself to your office network and the same thing can be done as you go home.
Very nice. With this, you don't have to manually change locations and settings when you go to the office or home.
I do this with Salling Clicker. If anyone already has that, I can upload the script that I wrote. (By the way, everyone who has a Mac should have Salling Clicker )
Well I did say if anyone had it already, not to mention that Clicker can do much more than detect proximity. You're right though, if anyone just wants something simple and free, that's probably a better bet.