There have been lots and lots of discussions of realtime scanning software on a variety of threads at ET over the past year. You will need to use the search function (upper right) and do a little homework.
I use First Alert. Ive been on it since 7/1999. It's cumbersome (no more than others, Im sure) but very flexible....it does not do historical back testing. Our firm also uses something called Insight. I have never used it but it can do same things First Alert can do. Since I have not used both, I dont know which is more reliable or easier or more flexible & "powerful" ....Suffice it to say, Im happy with First Alert ith all its idiocyncricies and bugs...I haven't touched 90% of what it can do.
I use Stock Watch Pro http://www.crontech.com/swp for scanning along with QCharts. I couldn't find anything else which allows formulas to be used in the scanner.
Try linnsoft.com. Pretty good prices and quick since the data is gathered and stored in your harddrive. Good luck
Try www.alertscanner.com if you use A-T or REDIPlus. I've found it's an easy way to keep track of when stocks I like to trade hit key levels. Getting alerts on thousands of symbols and frequently missing the ones that are important to me has always been a problem. It has a wide range of pre-programmed alert types that cover most popular technical indicators.