Ben Constable just blogs about another elegant way to listen to dependency property change, the trick here is using DependencyPropertyDescriptor, imagine that you have a Label called myLabel, and you want to get notified when it's ContentProperty is changed, then you can do something like the following:
DependencyPropertyDescriptor dpd = DependencyPropertyDescriptor.FromProperty(Label.ContentProperty, typeof(Label));
if (dpd != null)
// Add your logic here to respond to value change.
The other ways in WPF that you can use to listen to property change is to subclass an existing Control, and override the metadata of a dependency property whose property change you want to listen to, when you do so, you need to specify a PropertyChangedCallback which a delegate to your property change event handler, or instead of using PropertyChangedCallback, you can override the OnPropertyChanged method, and place your logic there, as a bonus, you can get additional information things like which property is changed by examining the value of passed-in DependencyPropertyChangedEventArgs argument's Property property.