but I wonder how long it would take in a remote area.
Doesn't need to be a remote area glenb. Airlines don't happen to have spare crews at every port.
Test at a port where no available crew:
Scenario 1. False positive Result: Flight Cancelled up to 180 pax affected. Pilot has the longest 24 hours wait of his/her entire career. Has about 2 minutes sleep in the process (wouldn't dare take anything to help settle the nerves and get some sleep!).
Scenario 2: Positive: Lets say for cold flu tablet. Flight Cancelled up to 180 pax affected. And the chances of this pilot keeping his or her job?
ZERO.
Its in black and white boys you have no come back on this one.