Like the other app, the text output area is flawed in that it doesn't scroll to the bottom when you get new output
From this I deduce that you are talking about the Terminal screen (in my BTInterface app).
The Terminal screen will mostly be used for debugging to see exactly what your microcontroller sent over the bluetooth link.
There is a limitation to the Terminal screen which I don't plan on changing just yet and that is that if a line of text is too long it is lost off the right hand side of the Terminal screen.
You do get to see a bit more if you orient to landscape and in the future I may make it sideways scroll but just now this is a limitation.
While the terminal screen is being viewed, and it can be called up even from standby by sending the string 'terminal' to BTInterface, you can send the command 'clear' to clear it.
I would call it 'input' rather than output, that is when you receive something from the microcontroller into the terminal screen I'd say that was input and when you enter something into the send field and press send, i'd call that output but tomatoes potatoes 
I did program it so that upon receiving 'input' from the microcontroller its supposed to scroll down to the last line automatically. Is it not doing that for you? what device are you using?
The Terminal screen can be used for collecting data from a user, you could switch to the terminal screen:
send("terminal");
issue the clear command:
send("clear")
and then tell the user what you want:
send("please input your credit card details");
send("so that I may syphon off a bit");
send("thank you");
and after all this setting up your sketch would be waiting for the user to type something and press the Send button.
In the future I may introduce other 'screens' and cunningly call them names like screen2 screen3 etc. but I feel it necessary at the moment to test the waters with a basic version of BTInterface, get people using that and then see what the popular demands are before making any radical changes, always trying to keep new changes backwards compatible.
I think this first version does pretty good. I may introduce flashy texts and bold and italic and all-singing all-dancing colours and perhaps even have it vibrate when you stick it in your pocket which will be nice but not until I have a clear indication of the direction that people want it to go in
When I get it to control my jet engine oh yes... I will configure screen1 to have just the slidebar (to control the throttle) then b1 will be 'Bendix On' (for the bendix clutch 12v motor that spins the turbine) and when I press it, it will turn the motor on and change the text on b1 to read 'Bendix Off' etc. then b2 will read 'Gas On' which activates the electric valve for the butane/propane starter gas cannister then b3 will read 'Glow On' which turns on the glow plug.
I'm thinking of making b4 into 'Auto Start' so it'll do it all automatically and get the jet running up to a reasonable speed because I put the engine on the back of my moped and its otherwise a bit awkward to do it manually when you're trying to navigate bumpy roads.
Jetduino 