[entangledqubit]

There are funds that trade on the rebalancing and entrances/exits of individual stocks from the indexes. While this may offer some yield, you can still get pulled under the bus by large scale movement in the markets... as seen recently.

While I'm not a fan of the "dark pools", if your "grandma" is a buy and hold anyway, the price of the asset should be ballpark correct most of the time since presumably the people doing the trades in the dark room are rational? I suspect that this setup is more useful if you need short term stability in the price to set up a complex deal.