PLB. A real one, not a Spot or Inreach.
Nail clippers to cut monofilament. I don't flyfish so that might not apply.
Edit: I'm a fan of these things for stuffing trash/line into instead of my pocket: Fishpond PIOPOD Fishing line Clip On Trash Can Orange https://www.amazon.com/dp/B003KQYY1W/ref=cm_sw_r_other_awd_x-vXwbB1NK883