I just reviewed a few files from a flight I took over the San Francisco Bay in a small plane with my Samsung Galaxy S2. Most clips are 29.97 but some vary.
I put the one that said it was 30.01 on a 29.97 sequence and it looked fine. Then, just to make sure, I interpreted it to 29.97 and it still looked fine.
There was lots of motion and some shots were bright (outside of plane) and some were rather dark (inside of plane).
So either variable frame rate is not as big a problem as stated, or it depends on the type of footage or the model of phone. I admit I was not trying to sync sound. The noise of the engine pretty much drowned out anything else.