I believe what you require is the list of all the enabled IME's on the phone and a way to switch to one selected, fullscreen/dialog/whatever can be your UI implementation and it won't matter.
To get the list of the the enabled IME's try this :
InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
List<InputMethodInfo> mInputMethodProperties = imm.getEnabledInputMethodList();
Once you have the list of input-methods, you can display them by name in anykind of dialog box and then switch to the selected one using the void switchInputMethod (String id)
function available in InputMethodService
class. The id
for a particular ime can be extracted from the InputMethodInfo
object that you retrieved earlier.