It ONLY works while the pogo app is running in the background, not when actively playing it or if it’s fully force closed.

It will NOT detect Pokemon that spawn or stops that refresh after the game is put into background running if your gps location doesn’t change.  It will only attempt to catch/spin anything that was currently visible before putting into background running.

It WILL detect Pokemon and stops that enter its detection radius from your gps location changing (either from walking, running, driving, etc or gps drift).

This appears to be intentional and not a glitch so as to promote either constantly checking on the game to allow Pokemon to visibly spawn and stops to visibly refresh before putting it back into background running or to encourage activity by removing yourself from a location beyond its current detection radius, even if only to move \~100m back and forth between two locations.

What this means:  

You can’t “camp” in one spot for hours on end with the game in the background for the device to work.  Either check on the game every 15\~30 minutes to allow Pokemon to visibly spawn on the map and spots to visibly refresh or get out and move around far enough to cause spawn/stop points to leave/enter its detection radius.

Additional note:  The stop spinner is so far working at speeds exceeding 35-40 mph.

PSA: I’ve been testing the Explorer Gadget since yesterday and have figured out why it “works” for some but not others. (More in text below)