Within the proximity actions app, you can assign a gesture to a shortcut. Tasker tasks can be called as shortcuts.
So you can make a tasker task to answer the phone (take call) and link to it within prox actions as a shortcut.
Likewise you can make a tasker task to kill an app (I think it requires root) and call that from a prox actions gesture, via shortcut.
I don't know for sure, but probably could do the same using automate also.