There is a product for Forex that has been quite helpful in learning to trade - ForexTester.
The product for stocks would mimic this.
The user would select a specific stock or criteria (a list as we get now with unisearch results). Lets start with a specific stock - easier to explain.
I take IBM and start on 1/1/10. I'm presented with a graph that I can add indicators to (like Graph). I'm given $100K in test money. As I click the space bar, the day's price appears. I can execute a buy or a sell. I click the space bar for each day until I want to execute another order or close my position(s) - full or partial.
It tracks my total dollars and gives me reports as I get with the backtester.

This accomplishes a lot for the trader:
1) learns the emotions of trading - what is it like when you're down 35% in July? do you keep to your system?
2) helps explore a specific system and allows the user to tweak it.
3) Lets the user see things a hard coded system may not
4) Improves the user's experience. In one day, a user could do 3 years or more of trades!