@Subterfuge and everyone else that this happened to -
I created an app for Android that will log all the stats to a file, it should help us get to the bottom of this. It's at https://play.google.com/store/apps/details?id=net.kwatts.powtools
Added stats include the sensor pads that are engaged and tilt/yaw/etc of the onewheel, current amps, etc. The app also displays all of these in one screen (and has buttons to set the ride mode and lights). I was riding and logging the other day and got the nosedive, stats showed going around 7 mph and both pads not engaged, although there wasn't a big spike in amps. Not enough data yet to figure out what is going on, but something is.