Deadman callout

Hi,

So I am a cave diver. When on site we will perform a check in/out with contacts before and immediately after the dive.  If we don't check out, after the expected checkout time a response is mobilized.

It occurred to me that on some of these more remote locations where no cell access is available (ie: mx) a deadman timer (DMT) feature would address this. 

Before the dive we set a 'max timeout' value.  If we do not return before the timeout occurs, when it expires it sounds a warning for 2 minutes (in case we forgot to disable the DMT and if no one responds to disable the alert, it then performs a SOS.

Just a thought..