Well, that's exactly it, simple solution... The player I use on android can adjust the A/V sync. Basically it delays the video by whatever amount you set to compensate for lagging audio. works great.
So now I just have to see if there is anything in the intersection of "video player apps that support adjustable audio sync delay" and "video player apps that can be remote controlled from another device e.g. a parent's phone". So far this appears to be a disappointingly empty set...
Anyway back to topic... my guess is that v6.0 is a month away, and that we will get:
* a very substantial overhaul of the satnav system, though probably not as sophisticated as taking into account elevation and weather to calculate likely range; just something that uses live traffic data and which proactively tells you about whether your destination is realistically reachable would be a huge step forward
* some new audio features (shuffle, playlists, maybe access to internet services that will just play what you ask for rather than building you a radio station themed around your choice)
* some new remote access features (if we are going to be able to name our cars then my guess is we'll also be able to send nav destinations to them from our phones, have greater remote control over more of their settings etc)
* maybe geofenced suspension height now that they've dealt with all their lowering/raising issues (since that really should be super-easy for them to add; mostly just some UI changes to help users manage the data)
* a load of bugfixes.
I would love for them to have fixed video overlay, to enable parking guidelines and generally make the UI do less weird things around the video, but I would not hold my breath.
FWIW the reversing guidelines/overlay on a current BMW 5 series are fantastically useful. As well as lines showing the car's trajectory based on current wheel angle etc there's a sort of "surface" overlay that gives even more detailed info about where you are as you approach an object. My brother in law has one and at the first attempt he can get his car perfectly parallel into a space that's only 10" longer than the car, purely by looking at the screen. Of course this sort of thing is a particularly British problem - we have very small parking spaces!!