Hand walkouts are great as a replacement to standing ab wheel rollouts. The eccentric or lowering portion is much slower and more controlled than using an ab wheel, so you'll be less inclined to tweak something.
It's also self-limiting: you can only really walk out as far as your core can control, so you aren't going to find yourself out beyond your level of capability.
Since these don't require any equipment, it's a great option for when you can't make it to the gym. You can also do them from the knees if the standing version is too difficult.