One of the best features of Quantopian is this concept of a strategy group. And the fact that one can specify, through their use of a universe, parameters that define one's group is just a wicked capability I've found no where else. Sure you can set screeners up to produce a dynamically re-generated group but what a pain. That said, the use of a gestalt metric, as compiled across a large enough group, I have found, produces excellent trend signals. It's the same concept as the A/D or TRIN. But when using your particular group (even as it changes within the universe) and applying your favorite market metric, when said metric drops below a threshold, beware the bear!
Grant's use of reversion could be augmented by taking the composite of the scores produced for each leg and using that as a risk on / risk off type traffic-trading-light. During risk off periods, one might either up the weight of your hedge, and or use the composite metric to dynamically shift more weight into your short side. I think I did something like this in one of the strats I built many moons ago... (Actually, it's for another S&C article coming out in April...) But effectively it's like this:
if (avgRsi > 50):
trendAdjuster = .05
else:
trendAdjuster = -.05
Simple right? Take the average RSI of your group of securities, if it's up, then shift the whole group's weight bias UP. This would reduce the shorts and increase the longs. The opposite when the average RSI is below 50. Such a deceptively primitive mechanism (but composed of hundreds of data points), can easily add a couple of percent to your annual return.