title: SharedPreferences between arbitrary applications
body: <p>Picture, if you will:
  Applications A, B, C and D.  All need to share some small amount of data between them but there is no guarantee that any of them will be installed.  That is, you may have B and D only.  Or A and C only, etc.</p>
  
  <p>Can SharedPreferences be used in this case?</p>
  
  <p>I understand that I can use createPackageContext to have A-D all use the package space of A, if A is like a master-app that is always installed, but what if I don't know which of these will be installed?  createPackageContext returns NameNotFoundException if used on a package space that doesn't exist.</p>
  
  <p>Do I have any content provider options in this case other than a file on the SD card?</p>