I'm not aware of any software specifically aimed at monitoring paper trades but maybe some of the portfolio managing software available on the market should be able to do the job for you.
Personally, I have set up my own portfolio manager in a Microsoft Excel spreadsheet. If you know your way around a spreadsheet it shouldn't be too hard to set up a spreadsheet manager to monitor your paper trading and measure its performance. You could customise it however you like and then build on it if necessary to monitor your 'real' portfolio.