You could use the sentiment indicators from various brokers etc., show you what % of clients in a pair are long or short.
There's an argument that if you take the contrary view to the majority the indicator shows, you should be in with a shout.
what do currency traders use since they aren't shown volume, then can futures volume be an analog?
I prefer trading futures, but sometimes have to keep skills in check with trade Forex, have two different data sources, one for forex and one from CME, so if trading Euro/USD, Volume of Euro futures placed under chart of Forex data, sometimes it is almost like cheating, LOL