We've featured Appium in the Radar in the past. It's one of the most popular mobile test automation frameworks. As we scale our test suite, being able to run our tests in parallel against an array of devices is key in having short feedback loops. Appium Test Distribution solves this problem very effectively with its ability to run tests in parallel as well as run the same tests on multiple devices. Among other things, it distinguishes itself by its ability to add and remove devices in which tests run without any manual setup required and with its ability to run tests on remote devices. We've used it in a few projects at ThoughtWorks over the last couple of years and it worked very well for us.