Once a niche tool only used by energy traders to help them place informed bets on oil supply, the services of tanker-tracking companies have lately been in higher demand. Although most of the industry’s customers still come from private-sector organizations such as trading houses who want to glean intel on oil supply and demand, geopolitical instability and the widening use of sanctions have enticed a growing universe of clients, including hedge funds and government agencies, to keep tabs too. That capability wasn’t widely available—or even requested from anyone not sitting on a commodities desk—a short decade ago.