There are a few ratios or even just amorphous relationships that give you the Mr. Miyagi inspired risk on/ risk off feeling. (And while I was not the first to reference the teacher from Karate Kid, neither were you so hold your comments.)
Here are two:
Copper/Gold - do a ratio chart of copper futures divided by gold futures or for you stock only types, the JJC ETN over the GLD ETF. When the ratio is rising, copper is beating gold and the feeling is that economic growth is beating hedging portfolios. That's good for the economy and usually good for stocks. It also keeps the dollar out of the equation since both commodities are priced in bucks.
Junk Bonds/Quality Bonds -Use the JNK or HYG ETF over the LQD high grade corporate. You can even use the TLT Treasury ETF in the denominator but when there is a flight to safety - as there was in 2008 - Treasuries are a different beast than just better rated bonds.
Guess what? Both peaked in February. Both ratios are falling. Both diverge from stock market trends.
Sell in May and go to the beach (If only I had a lucrative writing job).