People have been trying for years, but there's no substitute for a peristaltic pump. I went the more expensive route with a GHL profilux as I wanted some of the extra features, but there are ways to save a few bucks without sacrificing accuracy.
You can put together a quality 2 channel setup for < $200 now. The Bulk Reef Supply peristaltic pumps have a really good reputation in the reefing community. Rig up your own dosing containers, a couple timers, and you are dosing automagically.