Replacing the battery on an iPhone will be an expensive and nerve-wracking experience.
Apple revealed the details behind its iPhone battery replacement program this week. It's basically the same deal as with the iPod, in that you have to return the unit to Apple for battery replacement, but it's a little more expensive. The service costs $79 plus $6.95 for shipping to replace the battery on an out-of-warranty iPhone, and Apple says it will take three business days.
The service is also similar to the iPod in that all data is cleared from the iPhone during the replacement process, so you have to make sure that you back up all data on the device before sending it in. Apple says the iPhone battery is good for between 300 to 400 charges before performance will start to decline, which generally is the case for any lithium-ion battery over time. Usually for other phones, you can get a replacement battery and pop it in yourself.