Adam Strange is one of the more unique characters in the DC Comics universe. As he's just a mortal man that gets transported to another world, gets some of their armor, and then becomes one of its greatest heroes.
Ironically, Strange constantly transports between Raan and Earth via Zeta Waves. This makes him an asset to the Justice League, and thus Batman. In fact, in the Young Justice cartoon, the Zeta Waves were used on the Justice League Watchtower because of Strange's knowledge of them.
Strange is smart, courageous, and kind. He truly wants to protect Raan, and his wife Alana who he met there. This makes him reliable, and one that Batman can count on.