In my opinion, DXY is a very valid indicator but there are more instruments that show a high level of correlation with the market and can be followed. One of them is a highly speculative Biotech index .
Notice, while the market is running in a perfect bull trend, Biotech are in a correction after a massive dump in 2015-2016. In my opinion, Biotech has topped back in 2015 and a new massive decline can be closely monitored to determine the whole market´s top.
The specilative instruments are normally the first to fall as their growth is commonly built by hot money that rush into a same small door once any sort of a real danger appear. Obviously, one cannot fully relay on the speculators only as we all know how quick they can be on restoring their positions. But if a joint analysis will show a real bear at some point of time, speculative instruments decline should confirm a change in the trend.