In the spirit of Tim Cook's maniacal excitement about upcoming Apple products, I bring to you the shell script you can run repeatedly from the command line to check the App Store to see if Mountain Lion is ready for purchase.
This is what I used last year to check for Lion; it worked. This year, I update the search string to "Mountain Lion" instead.
As presented, it employs a 10-minute time-out, so you can run a repeat command with it.
curl -silent -A "iMacAppStore/1.0.1 (Macintosh; U; Intel Mac OS X 10.6.7; en) AppleWebKit/533.20.25" 'http://itunes.apple.com/WebObjects/MZStore.woa/wa/viewMultiRoom?fcId=489264329&mt=12' | grep -i "mountain lion" > /dev/null
if ($? == 0) then
say "MOUNTAIN LION MAY BE AVAILABLE"
Ready to improve the script? Have at it, campers!
Update: Looks like the URL changed from last year. Updated via Mark (mcackay).