I've asked a similar question here before.. I was looking for a good site to quickly look up information on an issue and I found comicvine.com, mike's amazing world of comics, xowcomics, and mycomicshhop.com to be very useful tools. Now I have a different but similar question.
What is a good mobile site for checking a book's value? I've always liked comicspriceguide.com, but if im using my phone it doesn't sign in, so I can't look up any information. I just want a tool that'll tell me the current going rates for a specific issue so I know if the one I've come across in the store is priced appropriately or if I should try to get the price down.