Also, how about PLB-406?

Ground distress beacons

The COSPAS-SARSAT 406 MHz radio frequency distress signal can be transmitted by hikers, backpackers, trekkers, mountaineers and other ground-based remote adventure seekers and personnel working in isolated backcountry areas using a small, portable Personal Locator Beacon or PLB.

I certainly know an AR15 would be a good distress beacon.