There are a surprising amount of things that can be automated for a complex aquarium. With open-source development boards being very cheap and eaesy to use, there have been many projects surfacing to tackle some of this automation.
"HCSCEO" built this complete unit for under $100.
The ReefBuddy, unfortunately, is dead. This isn't all horrible news though. The ReefBuddy started as a project to build a kit that would sell for under $100. To do this, the creators utilized open-source components like the Arduino for the brains. The creator, Steve, documented his build process and progress on this forum, allowing others to follow along and get excited.
When the project died, the schematics and PCB files were released under creative commons (about halfway down this page). If you are the DIY type and think you can do the Arduino programming, you could replicate your own Reefbuddy!
Here is the planned feature list from the ReefBuddy:
4 line LCD Screen
7 button interface
Screen and Buttons remotely mountable from the control box (Similar to Reefkeeper products)
4 switched inputs (can be used for ATOs, etc.)
16 available timers
16 switched 110 outlets (available in groups of four or eight)