My guild does a flask program for guildies wherein any member of the guild can buy a flask from the gbank at a discounted rate. I'm looking for an addon that would track the money they gave me for the flask and give me a reminder to put it in the Gbank later when I'm in a major city. Maybe a checkbox? Anything extra like what type of flask and how many would just be icing on the cake. Anyone know of anything like this?

This is very possible.

It can be hooked up to the various trade events and use TradeFrameRecipientNameText:GetText() to get the name of the person you are trading with. Ill see what i can do about developing an addon like this when i get time (no promises)

I use TinyPad for a lot of things, including tracking bank theft and ban lists for my guild.  You might consider it.  Last version I saw was on WoWInterface.