At this point the Archon, but it is a beta unit. It works with my computer, iPad and phone. Before that I was using the RKE. It had limited programming from the Internet.
The real question you need to answer first is what do you want to control, specifically, and why. Different controllers have different options available as well as different feature sets ranging from strictly monitoring all the way to full control as if you were standing in front of your tank at home.