A great invention that does already exist is the buckwheat nursing pillow from Brow Farm. It mans I am no longer straining my back and using one or both hands to hold the baby when nursing in the day. It actually works!
However, I am still very frustrated by slings. I even went to a sling meet to try and find one that supports the weight around your hips and allows you to pop the baby in and out easily without unraveling ten miles of knots, buckles and cloths. To no avail.
A bit of google time later uncovered something called a hip carrier (and it’s not cool, but nothing about baby care is cool) but this style of carrier only seems to exist in about three brands. It’s not been advanced far, but it consists of a sort of little shelf on a wide belt, so the baby can sit on the shelf bit at your hip. Some have a baby holding section that goes over the shoulder as well.
So then I thought, Hybridize! So this is a concept for a thing you attach to your waist and the baby can rest on it either sideways for nursing or upright for carrying.
Now I need to figure out if I can make one.