Issues with making a simple android app with unity ?

I am planning to make a simple android app with unity3d in which the users gets some sliders and scales a 3d model, before going ahead i want to ask you what issues i might encounter.

  1. Will the app be affected by different android screen sizes in market ?
  2. Will the users be required to install unity3D plugin first? if yes, can i bundle the unity3d plugin with the app.
  3. How big will the size be? (it will have 5-10 meshes and some GUI controls)

If you know of any other problems that i might run into by using unity for android development, Please add them in your answers too.

  1. Well, since it is 3d game, camera will simply show more or less of the world. (I am talking about aspect ratio)
  2. No plugin.
  3. It is easiest to try and build .apk and see.