The data from the HorN machines (as they are colloquially called) are very much analysed and compared against multiple criteria. Yes, staff do sometimes hit them as they pass through but no-one really has the time to spend doing multiple hits so there's minimal skewing and there's some statistical jiggery-pokery that smooths that out.

The most notable report I've seen was the before/after comparisons of Immigration following the expansion of eGate useage by additional countries.

The funniest I saw was on Friday afternoon going through T5 and the angry button was missing from one of the devices after security. I wonder if that was to dissaude people from selecting it, or was someone so angry they wanted to keep the button?

EDIT: forgot to say. in answer to the OP, the devices do have to be brought in for battery recharge/replacement, cleaning etc every now and then, so it's either temporary or someone has decided we no longer need to monitor the first wing