I like this planter design.
http://fivegallonideas.com/plant-seeds-without-hurting-back/NOTE: You do not need to use the plastic sheeting, shown in the pictures, on your planting beds. This device works on a bed that has been worked to loosen the soil to planting depth.
With care, this device should last for years. It could be made with a metal piece to punch the holes, at a distinct increase in the weight and effort needed to lift and place for each row. DO NOTE, that the cutting edge is made from a piece of pipe which can be re-cut and adjusted should it break off. Good design...
The whole point is avoid the need to spend hours bent over your seed beds.