As an adaptation to the Turtlebot I've added a button and audio user interface similar to the one on my larger robot. This uses an Arduino as a means of sensing button presses and communicating those to the netbook.
If you have a small number of locations that you wish the robot to visit then this provides an easy way to tell the robot where to go, which once it has been trained doesn't require that you run Rviz or need any separate computer. If two places are defined on the map then merely pressing the start button will cycle between them to implement a sort of fetch and carry.
Transporting things around within a building at slow speed is pretty much a business model in some scenarios, such as warehouses, hospitals and supermarkets, and could form the basis for more sophisticated domestic applications such as watering plants or dusting/cleaning surfaces like shelves or tabletops.
The button user interface is completely generic and doesn't necessarily require a Turtlebot. It could be used with any PC based robot which runs the ROS navigation system.