Startup Idea: Bidding Tracker and Profit Calculation Tool for Online Merchants

Startup idea to build a software tool for online merchants to receive reminders for bidding deadlines and instantly calculate profit margins considering various fees and taxes involved.

I am small merchant who sells stuff online and buys too. Now,Whn I am biding on stuff, I would like software to notify me through my pnone that it is going to end. So many times I missed so good bidding opportunity because I was not on time, or I missed, because I did not know my time is approaching. Other thing, As a buyer I would like to know, my profit, as soon as I post my item online, that means, I would like to know, after paying paypal, or company like ebay or tax, or whatever, How much the product will be in instant, so I can adjust my price, so I do not go in loss.