I would like an application which is not readily apparent to casual perusal of the Android. 

How best to activate it and bring its screen to the fore? Can I detect a special dialing sequence, like `*1234#`? Or a hotkey combination? 

When activated, I guess I can pop up an anonymous screen which does not mention the app, but only asks for a password.

If password is ok, then show the app.

Any suggestions?