Isn't that a bit risky? Won't updates erase the jailbreak? What if AT&T finds out? What if it renders the phone useless? What if?

 

If you want to send MMS messages to other phones that can receive mms you can send them like this
phonenumber@mms.att.net

I send my gf pictures in an email and she receives them seconds later as a standard MMS message. I can do the same to verizon users and many other services that have that enabled. Yes it's stupid it's not included but hardly an inconvenience that i worry about.
Iphone to iphone why not just email the photo instead anyway.

 

Update:

The trick is that it only works with people on family plans. So it does work... somewhat

 

Looks like I got one of these things just in time!

AT&T Launches iPhone MMS September 25 - iPhone MMS - Gizmodo