SwirlyMessage let you send and receive SMM/MMS from iPad 3G. SwirlyMessage for iPad is developed by the dev behind SwirlyMMS for iPhone.
“Send and receive real SMSes and MMSes with your iPad 3G.
To be able to use SwirlyMessage you need an iPad with a built in 3G modem. You also have to make sure that your carrier data plan allows for sending SMS and/or MMS. If you are unsure about this please contact your carrier.”
You iPad 3G MUST be jailbroken. You can jailbreak iPad using the guide linked below:
You can purchase and download SwirlyMessage from Cydia for $12.