A rather uncanny comparison, but some correlation observed... the SG Government Bonds are the next level "risk-free" instrument (perhaps not to all, but it is clearly one of the more robust).
Taking the SG10Y and overlay with SPY, some correlated trends are observed...
The yellow lines are the trend lines for the SG10Y, and break outs or break downs are triggers. From here, follow the SPY (blue plotted line).
Can be seen that when there was a break out of the SG10Y trend line, the SPY is bearish; alternatively, when there was a break down of the SG10Y trend line, the SPY is bullish.
Just noted that the SG10Y is just about to break out, so...