The popular ones in the market are as below:

Frank

  • Developed by Thoughtworks
  • Can only be used on iOS applications
Robotium

 

  • Can only be used by Android applications
Sikuli
  • Easiest to use among all because no scripting is needed
  • It works based on screen capture
  • Need to have separate tests for iOS and Android applications because of the different UI
Selenium
  • Most flexible. Can be used on both iOS and Android applications
  • Hardest to set up among all