Yeah that, IMHO, is the main problem with any iPhone-based solution: your data has to come over wifi, and so the latency and sync on that has to be fixed somehow. The equivalent Android-based setups use Bluetooth to talk to the OBD-II (and GPS), and the data's pretty decently synced already just because there's not much latency to begin with.
Harry's should be able to export vid+obd+gps data to
RaceRender 2 Video Processor as well, and then you can render with a nice custom layout, and RR2 makes it easy to fix sync issues as well.
Another random thing you may have noticed: Harry's is probably using the standard "Throttle Position" OBD-II code, which is actually unrelated to gas pedal position on our car (it reflects butterflies + VVEL info). There actually is a non-proprietary code for Accel Pedal Pos which would be more-useful on our cars. I can see it in any OBD-II app for the Android, except for my Harry's-equivalent (aLapRecorder) which uses the bad "Throttle" like Harry's does.