Incident detector

You dont need it open, but it does need to be running in the background of your phone. Which should be the default when installing Garmin Connect. The watch sends the detection alert to the app on your phone over Bluetooth. The recipients you choose will then receive a text or email.

Setting Up Incident Detection on a Garmin Device | Venu® 3 | Garmin Customer Support

Redsprite said:

is this different to having just the tracking on?

You don't need to start an activity to have incident detection work 

Thanks for this, think I’m a bit dense but  running in the background?  I leave the tracking on all the time so I go  a run,start the watch is that it? 
I know it’s activated before when I  a fall and that was brilliant but don’t recall having the app running , sorry if I’m confusing you 

If it worked before, then you're good to go. The app is running in the background on your phone even if you close it.

Thank you