I'll check it out. But from your description, it sounds much more than what I am looking for.
I saw one a while back at a local irrigation parts store that was real simple. It was made to be installed right on the line. You attached a pipe on the inlet, water mixed with fertilizer inside a canister, and then you continued your pipe at the outlet. Just lift the lid and add more fertilizer as needed.
The store doesn't sell that model anymore. But that's what I am looking for.