I found a really nice overview about Open Source Mobile Testing Frameworks for Test Automation. The overview was created by Dominik Dary (eBay). In his table he showed how many test automation frameworks are currently available for Android or iOS testing. The complete blog post can be found here:
http://www.dary.de/2012/03/open-source-mobile-test-automation-frameworks
A big thank you to Dominik, who provided this overview!