afaik, it's only possible on the original devices that had the S5L8900 CPU (iPhone 2G, iPhone 3G, and iPod Touch 1G). I don't think open iboot has been adapted for the 24kpwn devices. Any devices newer than that (fixed bootrom 3GS, MC model iPod touch 2G, ipod touch 3G, iPad, and iPhone 4) definitely can't run android until a new bootrom exploit is found.