Effective December 29, 2014, US citizens traveling to Germany have an opportunity to speed their entry into Germany, using Germany’s EasyPASS system. 
German citizens traveling to the US likewise have an opportunity to speed their entry into the US using the US’s Global Entry system.
Here is a page describing how this new program works for US citizens.
To register for EasyPASS, U.S. citizens must visit an enrollment center operated by the German Federal Police in Germany. Enrollment centers for EasyPASS can be found in Terminal 1 at Frankfurt Airport and in Terminal 2 at Munich Airport. To qualify, U.S. citizens must have an electronic passport (epassport) and be at least 18 years of age.
Here is a page describing how this new program works for German citizens. Importantly, a German citizen who has the patience to go through the many required steps will benefit not only from expedited entry into the US through Global Entry, but will also be eligible for the TSA’s Precheck program.
There are already similar reciprocal trusted traveler programs between the US and:
- Canada (see this page)
- Mexico (see this page)
- Netherlands (see this page)
- Panama
- South Korea (see this page)
US travelers who belong to Global Entry enjoy expedited entry into these countries: