TaintDroid is a project which should show which Android applications send information to servers. The scientists who initiated the project made some interesting discoveries: out of 30 Android apps, half send location data, some programs also send data such as the device ID or phone number. In order to use TaintDroid, the Android OS has to be adapted, so it's not a tool you just install on the side.
It is to be hoped that the developers of the applications will now move on to collecting a little less data. The free Android platform should actually benefit from the fact that there are fewer privacy issues than, for example, Apple, but such discoveries do not exactly strengthen this image. Maybe developers will also start to put a "We do not collect data" seal on their applications, which could then be verified with TaintDroid.
More information about TaintDroid can be found in PDF of the development team.