This Chrome extension allows to create an email notification when an application price drops from the iTunes AppStore !
How do it work ?
Install this extension, and start browsing appStore through the iTunes preview pages.
For instance click this link http://itunes.apple.com/us/app/dx-hot-deals/id414197747?mt=8 and start browsing iTunes preview
Your Chrome browser will automatically detect you are browsing the iTunes preview and will add a small green icon on your address bar, click this icon, and enter your email address, that's all folks !