Kyle, I use Aquarix, and frankly it's a godsend. If I actually have a clue as to what I'm doing, it is because in my first few years of this hobby I recorded everything - I mean EVERYTHING - I did to the tank in Aquarix. So when I had questions about what was happening, or what was going on when THAT particular algae hit, or before my XYZ fish died... I KNEW what the conditions were that may have lead to the event.
It was a very valuable tool to me in my learning.
If you are thinking about implementing something like that, IMO AQUARIX is a good place to start looking at a functionality. Personally I'm big on the event tracking and tank stock tracking (fish, plants, inverts). All the other stuff (financial tracking, reminders, charts) is just fluff IMO. Being able to record what you did, and then look that up later is it's greatest strength.
If I were to improve it, I would make it more able to record various measurements (like Potassium - not included in things it will accept a value for), and have a default mechanism for recording quantities of ferts (by type) added.
If you build it, and it's better than Aquarix, I for one, will use it!
Steve - 33g reef and a 180g planted in need of a re-scape.