What switch was Skiles talking about shortly before the Hudson landing?
It's explained in the final report. Most definitely they asked him what he meant, as the transcript itself is:


  * * switch?


"*" denoting unintelligible words by the transcribers.


  The first officer was referring to the cabin emergency notification switch, which provides a signal to the cabin crew members indicating that an emergency has occurred.


To which Sully replied "yes", then the GPWS announced 30 or 50 (transcribers not sure), then the RETARD callout (for the thrust levers) was announced (computers eh). The recording ended about 5 seconds after asking about the switch.


(wikimedia.org)

Putting the switch to ON does three things:


lights the overhead emergency lights (more here on this cabin indicating system)
lights the exit signs
lights the exit markings on the cabin floor (proximity marking system).


Regarding the HOT and CAM, see: What is the meaning of HOT-1, HOT-2, CAM, etc., in cockpit voice recorder transcripts?


  CAM Cockpit area microphone voice or sound source
  HOT Hot microphone voice or sound source
  -2 Voice identified as the First Officer


The audio source indicated is usually the clearest one.