when(.UIKeyboardDidShow) { note in
    // do stuff 
}

when(.UIApplicationDidBecomeActive) { _ in
    // do stuff
}

// define the custom event name
extension NSNotification.Name {
    static let somethingHappened = Notification.Name("somethingHappened")
}

// send your custom event
trigger(.somethingHappened)

when(.somethingHappened) { _ in
    // do stuff
}

trigger(.somethingHappened, userInfo: ["goodTimes": true])

trigger(.updatedFromRemote, on: self)

when(model, does: .updatedFromRemote) { _ in
    // do stuff
}

// make sure the closure is run on the main queue
when(.somethingHappened, doOn: OperationQueue.main) _ in 
    // do stuff
}