Are you talking about brine shrimp hatcheries?
You could definitely make something for this. A plastic container that you pump a small amount of tank water into and let it overflow into the display (it would have to be higher than the tank of course). Drop a cube of food in and it will slowly drop into the tank as it thaws.
I don't know of another way to feed frozen foods over a period of time.
I have used a dosing pump to feed live foods that were stored in a mini fridge before. It was for a seahorse tank.