I created this question, because it is a very specific series of steps required for me to get any data showing in the logcat, and maybe you're having the same issue testing on external devices.
The order is:
- Launch app on external device
- Start new GenyMotion emulator (shouldn't matter which one)
- Change logcat to show "No Filters"
- Switch logcat to emulator (should start showing data within logcat from emulator)
- Switch logcat back to external device
And voila! It should be pouring out data from the external device. It only works on the "No Filters" setting, so it is a little tedious to find crash reports and anything else pertaining to the app, but it's the only way I can get the logcat to work with my external device.