"Update" your iPhone to Froyo without the use of computer
Some people are so excited by Android that they even found a way to run Google's mobile OS on your iPhone. While this process is fairly easy, it was further facilitated thanks to Bootlace 2.1, as you don't even need a computer to do the trick anymore.
The only downside is that the Froyo treatment is only eligible to the original iPhone and iPhone 3G, while the cream of the crop among the Apple devices – the iPhone 4 and the iPhone 3GS – will have to wait a little longer.
Sadly, there is no information how long it will take to run Froyo (or the future versions of Android) on the newest Apple devices, but if you want to run Android on your iPhone or iPhone 3G, follow the instructions that you can find in the link below
source: Redmond Pie
The only downside is that the Froyo treatment is only eligible to the original iPhone and iPhone 3G, while the cream of the crop among the Apple devices – the iPhone 4 and the iPhone 3GS – will have to wait a little longer.
source: Redmond Pie
Things that are NOT allowed: