I used this developers app with my P2+ and it worked great! He puts a lot of work into his app for sure. I haven't tried this one for either my P3A or my inspire because it seems DJI keep screwing thing up on their end with the firmware.
You have to install a specific sdk firmware to use it so don't expect it work with any of the DJI firmware updates.
I haven't been following it much lately but here's a link to the google group that will answer all your questions. If you're interested just sign up and check it out.