Android - shared variable between apps

Android - shared variable between apps

I'm building a shared library that can be shared in many applications
I need global variable that all apps using this library can write and read
the variable.
I check the solutions:
1) shard preference - irrelevant, because I do not have a standalone
application. 2) content Provider- irrelevant, because I do not have a
standalone application. 3) SQLite DB - irrelevant, because I do not have a
standalone application. 4) file in SD card - problem if there is no SD
card.
Does anyone have an idea how to do it?