NVP offers something like this in his correlator thread. You could differentiate the basic deltas on all the major pairs and come up with a standalone currency line for each, but it would be rather coarse.
At it's most basic you could look at AUDJPY, AUDUSD etc for all of say the 8 majors and for each of those 28 pairs decide, in whatever way makes sense for you personally, whether that pair it trending up, down or not trending. For those trending up assign a +1 to the primary currency and a -1 to the counter-currency. Reverse for a down trend. Zero for non-trending.