I’ve just released the initial version of an Appium Maven plugin.
The code is on Github: https://github.com/Ardesco/appium-maven-plugin
Feel free to give it a go and post any issues/feature requests on Github. Hopefully it will be of use to lots of people.
I still have a bit or work to build in support for all the Appium command line switches, and I need to add more documentation. But the basic instructions in the README.md should get you started.