I like this scanner, and have been using it for about a year now. I actually used another version of it for the first six months, which is available at mtrader.com
Both scanners were developed by Mike Diplock, who lives in the UK, and they only scan for Nasdaq stocks. This scanner also requires a Realtick feed and high speed internet access.
The scanner does not actually "Read the tape in Real Time" but uses the opening and closing prices of one minute candles to perform the calculations. The scanner is divided into two windows, one for your "Watch List" and the other for Alerts. The watch list is great, because you can filter for stocks based on volume, price, pace, speed, and other parameters. Mike Diplock defines "Speed" as the rate of buying or selling in a stock. Buying is represented by a positive number, selling by a negative number.
Since I only look for stocks that are selling, I can set my watchlist to view only stocks that have a negative speed and that also meet the pace, price, spread, and volume requirements I specify. This is great, because I have a watchlist that I sort on speed, updated every minute, that gives me the all the stocks that are selling on the Nasdaq, from the fastest to the slowest. I think this is much more helpful then Greatest gainers/losers lists, etc.
Another cool feature of this scanner is you can drag and drop a stock symbol from the watchlist or the alert window into Realtick.
I also programmed my own alert to find fast selling stocks which works great. They also have pre-progammed alerts that work pretty well.
I would recommend this scanner because it is not too complicated and can be learned, although I will admit I put a lot of time into learning all the functions so I could really understand how I could use it to my best advantage. I would also recommend that every trader use some sort of scanner and understand it intimately, it will definitely give you an edge in finding stocks that meet your criteria.
Alex