If you have an iPhone 2G or 3G handy and you're not too fussed about a spot of jailbreaking, it's now possible to installdirectly on it, without the use of a computer.
You could already install Android with a tool called iPhoDroid, but that needed a PC. Now you can do it directly, thanks to an application called Bootlace, and the wonderfully named funkyspacemonkey.com has posted full instructions. After jailbreaking your iPhone 2G or 3G and installing the app, you'll have a dual-boot iPhone.
This is exactly the sort of thing that gives Steve Jobs palpitations, and completely makes any warranty you have void, dead and cancelled. But jailbreaking is perfectly legal, and frees your phone from Apple's restrictions, which means you can download apps you wouldn't normally have access to from installers such as Cydia.
For iPhone 3G owners, jailbreaking might not be any worse than what the, as it made the device unusable for many people. The imminent iOS 4.2 update may solve some of these problems, however. iPhone 2G owners are pretty much stuck on iOS 3.1.3, and jailbreaking could free you to have a little more fun.
This leads to a rather curious situation where some iPhones will have Android 2.2 before some Android phones. The Sony Ericsson Xperia X10, for example, is only just having. On a side note, the iPhone only has one button, so we believe it repurposes the top button and volume rockers to give you Android functionality.
We haven't tried it, but we hear it doesn't run quite as smoothly as it does on an Android device, understandably. But if you're a curious iPhone owner, or want to play a particularly cruel practical joke on one, give it a go. Just don't go crying to us when Jobsy gives you the evils.