The ACR C-Strobe — a high-visibility rescue strobe with an integrated whistle, for attaching to a lifejacket or pack.

Light and sound are a better pair than either alone. A strobe is visible for miles across open water or an open valley at night; a whistle carries around corners and through trees where line of sight fails.

Manually switched rather than water-activated, so it works equally well on dry land — a stalled vehicle on a shoulder, a night walk out, a camp that someone needs to find.

Clips on and stays there. Thirty dollars for the two signals that cover night and bad visibility.