An app called Tablet Talk can handle SMS and MMS, and it also allows you to make and accept calls from the tablet. It works over WiFi or Bluetooth, whichever you prefer. However, it doesn't actually transfer audio from phone calls to the tablet, so you would need to either use your speakerphone, or connect a bluetooth headset or car kit to the phone. This is a limitation of Android, unfortunately, and so far, nobody has found a way around it. I'm sure it will be implemented into Tablet Talk once it's possible, but there's no telling how long that will take, or if it will ever be possible.