Tesunho Mobile radio with 8-pin secondary development Jacks. 

A client use it to connect with a temperature sensor in a refrigerator truck. To send a SOS alert when the temperature falls below a pre-set parameter.

Trigger the SOS from external source via accessory plug, suitable for many applications. Like, foot PTT, foot SOS button-when you're in danger, may not able to send SOS by your hand. A covert external SOS button (underfoot or other safe&convenient place) would be greatly helpful. 

Welcome to inquire if any ODM demands. Tesunho professional R&D team at your services.