I use TabletTalk; you need an Android phone though as it sends/receives TXT/MMS using the phone as its modem.
Can also send and receive calls with it, although again, the audio comes through the phone. Not a problem if you have a BT headset; and there's also an option to answer with the phone's speakerphone.
Has a dialer, call log, message inbox, etc, all like it was running on the tablet itself. Integrates and acts like a native dialer for apps.