GMailChecker is a java midlet that can be installed on your phone and used to check your new messages in your GMail account. It requires the use of the GMail-provided Atom feed. Using this feed, it will present the new email in your Inbox. It has only been tested successfully on a few phones: Nokia 7610 & 6600. It does not work on the SE P900. Try it out and let Martin know where it works and where it doesn’t.

Source: GMail Checker