There are dozens of custom ROMS which allow you to run modified versions of Google Android on a variety of smartphones. Don’t like the software that came with your HTC Nexus One? No problem. Just pick an alternate ROM that has the features you’re looking for. Want Android 2.1 on your HTC G1? Yup, you can do that too.
But what if you want to have the best of all possible worlds and run several different custom ROMs on your phone — at least until you decide which you like the best? Well it turns out there’s a way to do that too… although it’s still a work in progress.
Independent developer punk.kaos has released a tool for the Droid Eris that lets you boot a ROM from the phone’s SD card instead of internal storage. This lets you load one version of the operating system on your phone while carrying another on your SD card.
If I’m reading the instructions correctly, it’s not as easy as picking which ROM to boot from a menu at startup. Instead you have to modify some files to switch between ROMs. But it’s a start.
For the most part, punk.kaos says that Android runs just as well from an SD card as from internal storage, although you’ll want to stay away from slower SD cards. While the multiboot tool has only really been tested on the Droid Eris, it should be able to run on at least some other Android phones as well.