A few things that you can't do in the official app, but you can do in the Teslabot: (1) voice control - send a voice messages/commands to Teslabot, (2) find out whether your car can go to a destination such as San Francisco with the current charge - Teslabot figures out location of the car, distance to the destination, battery range and answers that question, and also the bot is available from your laptop/desktop.
I was wondering the same thing.. I understand that there are some additional features, but what is keeping Tesla from providing those features in a future app update? This is a cool product, but I wonder about the ability of it to compete with the official app, especially when they are relying on Tesla's API.