I was a guest on the Geek.com podcast that my buddy Joel and I recorded this morning. We talked about all things mobile and I mentioned that I had an iPhone 3GS running with my T-Mobile SIM in it and was able to use MMS with the native iPhone text messaging application. Joel thought this was pretty slick and asked if wanted to put together a guest post on the subject and that post is now live on Geek.com.
As you can see, if you have an iPhone 3G or 3GS that is in another country that supports MMS or a jailbroken one with a T-Mobile SIM you should be able to view and enter the proper MMS settings to enjoy photo and video messaging on your iPhone. I expect this is exactly the same functionality we will see when AT&T finally rolls out support for MMS, but for now check out a few of my screenshots to see what it will look like on your iPhone.