Know of at least one two way communicator that has a dead man's switch.

https://www.ybtracking.com/ aka Yellow Brick, made over here in the UK. (See these on expedition, trek and survival TV shows quite often, recently an Alone US contestant called it out by name. Presumably because they can be rented for events.)

Have to press a button every X minutes to prevent an emergency alert being sent.

Just not going to get much change from $700 for the basic model.