Free stuff is always nice! But this isn’t just free it’s included in Lion. You not only can monitor your Mac’s wifi but also your wifi network. Check out what Macworld had to say and how to get it. Or here is an excerpt from their post.
“Wi-Fi Diagnostics is tucked away in the /System/Library/CoreServices folder. To get there, I pressed Shift-Command-G in the Finder (the equivalent of going to the Go menu and choosing Go to Folder), and then typed in the /System/Library/CoreServices path and pressed Return. Once in the folder, I found Wi-Fi Diagnostics and double-clicked it. Alternatively, you could launch the Terminal and type open “/System/Library/CoreServices/Wi-Fi Diagnostics.app”, and then press Return.”
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