Jailbreakers have already cracked iOS 5's Notification Center widgets, according to 9to5Mac.



From TUAW:

Notification screen widgets are little apps -- or widgets -- that run in the new Notifications Center in iOS 5. iOS 5 will ship with two widgets, stocks and weather. However, as usual, the jailbreak community wants to push things forward faster than Apple does, and they've already come out with a host of third-party widgets.

  iOS 5 jailbreak offers third-party Notification Center widgets