http://www.macrumors.com/2015/04/21/apple-watch-developers-guaranteed-device/:

“We want to help give Apple developers the opportunity to test their WatchKit apps on Apple Watch as soon as it is available. You have the chance to purchase one (1) Apple Watch Sport with 42mm Silver Aluminum Case and Blue Sport Band that’s guaranteed to ship by April 28, 2015.” Perfect for testing our Apple Watch games Berry Quest, Blackjack Mini, and Football Twos.