Can I auto-rotate the screen 180°? Is there any way to make the Android 2.1 automatic screen rotation rotate all the way up to 180°, instead of just 90° either way? I would very much like to be able to use my phone upside down, because the audio jack is on top. 

I've looked all over the web and the only advice I found was to install a custom rom (like Cyanogen,) but I haven't found any builds suitable for my Samsung Galaxy S.
I do not believe Android 2.1 allows this. I've read that the latest release Android 2.3 (Gingerbread) will have this feature.

Sorry I couldn't find the post that mentioned it but here is the API link.