CarrierIQ software is installed on roughly
150,000,000 cell phones. It is supposed to
"enhance the user experience" of these
devices but Android developer, Trevor Eckhart
has alleged that it can log an array of activities,
including text message content.

In addition to being difficult to detect, Eckhart
found that CarrierIQ could not be uninstalled,
as shown here (he and others have since
developed apps for removing it).