MobileMe, Yahoo Mail and Exchange have had push email on the iPhone for some time, but until now, Gmail users were left out of the party. However, a developer has coded an application that could rectify that.
Push email is where emails are "pushed" to your device, without having to go through the cumbersome process of checking with an external server - something that consumes CPU cycles and battery life.
The app is called GPush, and uses new functionality in the 3.0 firmware to notify you whenever a new message comes in. Just run the app once, put in your username and password, and you're all set.
Whether or not Apple approves the app is yet to be discovered, though technically there's nothing in either Google or Apple's small print that should forbid it. If it does go online, it'll cost $0.99, which will probably translate to 79p over here.