  We present an add-on for the Android platform, capable of intercepting nearly
all interactions between apps or apps with the platform, including arguments of
method invocations in a human-readable format. A preliminary performance
evaluation shows that the performance penalty of our solution is roughly
comparable with similar tools in that area. The advantage of our solution,
however, is that it is truly modular in the sense that we do not actually
modify the Android platform itself, and can include it even with an already
running system. Possible uses of such an add-on are manifold; we discuss one
from the area of runtime verification that aims at improving system security.
