+1 RaceChrono on my phone with a external GPS that's a QStarz 5hz and OBDLink MX.
I just set it all up at the start of the day, make sure everything is paired up and RaceChrono is running and then let it record for the whole day. I don't turn off the GPS throughout the day and the battery lasts the whole day easily.
I also walk off with my phone and when I get back everything automatically pairs up again.
Finally I use a GoPro for video which I do need to remember to start and stop every session.
Overlay is done with RaceRender. A bit finicky finding the start point but otherwise all works well.
My video at Phillip Island:
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