Baby carrier - NON car seat?

Hello all, I am wondering about baby carriers - NOT a car seat, and NOT like a sling etc. But something like a removable base carseat, but not a carseat. Confusing, I know. We just brought baby home, and my wife needs some ideas for this, because if she goes to an appointment, she doesn't want to try and figure out where to put him if she has to put him down for said appt. (Mostly like dr appts.) Any ideas or products to mention would be wonderful, thank you!