This application is called TexTab and with it, you are able to send text messages (sms). Actualy it is more like an interface to let you connect to your phone and let you send and recieve the text messages on your tablet.
You can download it and find out more about this application from the developer, howettl‘s app thread opened on XDA-Forums, like app features, changelog and upcoming features.
“TexTab is an SMS app for Android tablets. It allows you to connect your Android 2.1+ tablet to your Android 2.1+ phone over Bluetooth and send/receive SMS messages on your tablet as if you were sending them from your phone.
I’ve been working on this app for some time now and I feel that it is ready for public beta testing. I encourage everybody to download and install the app on both your phone and tablet, and please provide feedback here.”