StockDaddy was created as an answer to Google Finance shuttling their excellent Porfolio Tracker. I love being able to glance at my portfolio in real-time throughout the day (unless the market is down) and felt their was a need for a simple free portfolio tracker. I started messing around with the GOOGLEFINANCE() function in Google Sheets and made a very simple tracker that updated every minute. That was neat, but moreso, it showed me that I could port this to the web if I could find a data source.
That's when I came upon IEX and their excellent API for real-time stock prices. The rest was just a matter of porting what I had done in Google Sheets over to the web. That took a bit of work, but I was able to craft the site exactly how I wanted it, including performance on every holding across multiple portfolios (including dividends). Having an annualized return calculation was important to me as well. It probably took 3-4 months of long hours of coding, but once I was done, I decided to open it to the public.
Hopefully you find some value in it.