The Dark Index (DIX) is a dollar-weighted measure of the Dark Pool Indicator (DPI) of the S&P 500 components. When the DIX is higher, market sentiment in dark pools is generally more bullish. When the DIX is lower, it is more bearish or uncertain.
Gamma Exposure (GEX) is a dollar-denominated measure of option market-makers' hedging obligations. When GEX is high, the option market is implying that further gains are unlikely. When GEX is low, volatility is high, but further losses are unlikely.