I have used in-field recordings as a way of reviewing my field technique for many years. Time and again I find when I'm flowing well during a sarge I simply can't remember what I said in any great detail. This is because in a good sarge one tends to be in the moment with an outward focus rather than thinking through what you are doing in minutia.

Starting with audio back in England, I recorded sarges, some extending just to opening and others recording the full monty !close.

Video is also proving to be a good tool in that it records the interaction more fully. My current video recording system is not hi-tech but it tends to catch the target's reactions at a high enough quality level to capture facial and non-verbal responses; albeit at a lower sound recording quality than with a dedicated recording device.