Identify this “thing” which caused major false alarms in U.S cities in early 2007

Cracked by: bobo , Poornima , sidsen , udupendra , teju , bs , Dibyo , Abhishek , Tathagata Chatterjee , vijayaraghavan and alephnull.

bobo, Poornima, sidsen, udupendra, teju, bs, Dibyo, Abhishek, Tathagata Chatterjee, vijayaraghavan and alephnull