Don`t know who " invented " the spod but we where useing home made ones back in the 80`s made out of plastic bottles , could`nt get the distance of the modern ones today becouse ours where bigger and a lot lighter .
I would`nt say its the same as a swimfeeder , the swimfeeder will take your bait down to the bottom and spread your feed over a very small area ( on a lake ) were as a spod will spread your feed from the top layer of the water and depending on the weight of your feed , depth of water , could spread from 2 feet - 10 feet or more .