When the heart rate monitor on Keamy's arm is shown closely, it is obviously a Korg MA-30 metronome.
When Kate meets Jack at the beginning of the episode, her car has California tags but a Hawaii safety inspection sticker, since this is where the show was filmed.
At various points in the episode, each time someone raises a rifle, a racking sound is heard, although only few of the people seen actually rack their rifle. It would be illogical anyway to wait with loading the first round into the chamber until raising the weapon. Especially Keamy's party surely does not go into combat with unloaded weapons. The racking sounds are only added for dramatic purposes.