I saw that this did not yet have the answer that I originally wanted to find, therefore, although it is a little older, here for future Googlers:
Download the jar from https://developers.google.com/mobile-ads-sdk/download
Put this in your pom.xml (with the appropriate version of the course):
<dependency> <groupId>com.admob.android</groupId> <artifactId>ads</artifactId> <version>6.4.1</version> </dependency>
And then run this in your shell, again with the corresponding version name / jar:
mvn install:install-file -Dfile=GoogleAdMobAdsSdk-6.4.1.jar -Dversion=6.4.1 -DartifactId=ads -DgroupId=com.admob.android -DgeneratePom=true -Dpackaging=jar
Keep in mind that the above command has a version that needs to be changed in two places - once in the file name and once in the -Dversion parameter.
It might also be a good idea to include the latest version of the library in your project and have something like the following in your pom.xml above the dependency, as this is not the step that you will probably remember if you should google it;)
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