Up until recently there was no way to receive push notifications for e-mail through GMail on the iPhone. However an application called GPush has been added to the iTunes App Store earlier this month.
Push notifications are one of the biggest advantages that BlackBerry mobile phones had over the iPhone before the iPhone OS 3.0 was released. The application does not open or send e-mails, it literally only sends push notifications. GPush was developed by Tiverias Apps.
GPush is easy to set up. All you have to do is submit your user name and password. After entering the information, you just have to agree to let the app send you push notifications. The application still has several bugs, but it still works pretty well.