signals
Visual Signals Are Key For A Rescue At Sea
No matter how big your boat is when you are lost you are a small object in a large ocean.
One LED Flare Replaces U.S. Required Pyros, Sirius Signal But Not Ocean Signal (BLOG)
Given that the cheapest flare set costs about $33 and expires 42 months after manufacturing, the Sirius substitute may be a "no brainer."