From OXCGN:
"Gears of War 2 is almost here. To celebrate the release, 7 COGs have been placed around Australia in secret locations as well as 7 in EB Games retailers, 2 virtual COGs on the EB Games Australian Website and another 5 virtual COGs on IGN.com.au. These metal COGS allow you to unlock the secrets behind the epic back story of Gears of War 2. There's only 1000 of these to be found in the world guys, and only 50 in Australia and New Zealand!
Physical COGs are marked with unique codes that when punched into the Gears of War website unlock content that tells the epic story between the conclusion of Gears of War and Gears 2. Each time one of these COGS is found a new part of the 'Last Day' story will be revealed on the Gears of War website."