We use blankets, people have been using blankets for alot longer then grobags have existed
There are guide lines about using safe sleeping that include blankets
things like making sure baby is in feet to foot position (feet at the foot of there bed) tucking blankets in under the matress (so baby can wriggle out but not move the blanket)
You place half the blanket right under the matress going the whole width then lay baby on matress and then tuck blanket under other side, because the blanket is under the matress the babys own weight is keeping it from moving
Tucking blankets under the babys arms so arms are free so they can not pull the blanket over face (obviously hard to do if swaddling)