Thanks to both you and MatGeorge for the recommendation on the VLC player. It is a useful alternative to have.

In this case, though, the actual .mP4 file that I received looks roached and doesn't play in anything that I've tried thus far. I brought the file up in a hex editor and the first 307 MB of it are all zeros with seemingly no mp4 header info that I can see.

Thanks.

I'm in the same boat as you. Here are a few of things that I do while driving or while stationary but without a guitar in hand:
-On Pebber's you-tube channel, in the Isometrics_Part_1A at 6:10 he mentions some things that you can do while driving.
-Since I play left-handed, I can use drive-time to practice trills on the gear-shift, but this could be done on the steering wheel.
-I use my cell phone as a guitar neck to practice spider exercises. I learned several of the more difficult ones this way.
-I carry picks in my computer bag and will practice the scalpel movement pretty much anywhere.
-I've got a small practice guitar that can fit in a carry-on bag so I can practice at night when on the road in a hotel room. Put a metronome app on your cell and practice anything to that even if it's just learning how to tap to odd-time signatures like 5's, 7's, etc.
-I listen to the radio in the car and will figure out and finger the chord progression as I hear it. I don't have perfect pitch so I may be fingering the wrong chords, but it does help me develop my ear which is always useful. Or I'll try to finger or sing the bass line.
-I will attempt to sing intervals so that I build into my head how a maj 7th or a #5 or other intervals sound so that I can recognize them on the fly.

Eggman