Since I am building a german Echo-class airplane, an ELT (Emergency Locator Transmitter) is mandatory. This ELT has an acceloremeter inside and can detect a crash. After activiation it sends out a signal on 406 MHz as well as on 121,5 MHz. Satellites will detect this signal and a rescue mission is started.
I bought the ELT ACK E-04 which includes a remote contral and an antenna.
The picture shows the ELT mounted in the recovery system compartment (from above). Remote control with an audio alert indicator is mounted in the instrument panel.