I I just bought a Kenwood car stereo deck that indicated on the box and in the manual that there was Android compatibility. Got the thing installed, plugged in my S5 with 128GB microSD, and I got "NA Device." I did some research and it turns out the damn thing doesn't support MTP. WTF? MTP has been around since ICS, maybe a couple years. I would think that a BRAND NEW car stereo would have MTP support. /rant
Anyway, I tried various apps on the Play Store, and SGS3 Easy UMS, and none of them worked. One or two mounted the external card as an empty CD-ROM drive. Is there any way to get UMS working?