i tried it worked...it works on 2G..i phones only right now..

source: http://www.yeahgadget.com/2010/04/android-os-on-an-iphone-hackerdavid-wang.html

David Wang has made it possible. He has posted a video of David posted on his blog
on how to make it work on any 2G iPhone device.He has made the source
code downloadable and gave an instruction how any one having Ubuntu
32bit OS can easily install the Android OS. More better news is that it
runs a dual boot, which means you can either use iPhone OS or Android
OS. Preety cool, huh.

David have also asked for volunteer to help with this project and its not a surprise that many have already responded.

Check out his video how the Android OS works on iPhone.