The idea was so tempting that I went ahead to test that into my program with C# and IB. The first thing my computer said to me was "transaction with net position negative one" when a limit sell order was transacted. It was a monotonous emotion-free female voice. The emotion-free part is kind of creepy. I am still working on adding more "emotion" and "urgency" when level 2 prices are hit. All the jokes aside, what you want is possible. I had fun just thinking about the idea. Though I advise you not implement automated trading just yet because it may not be ready. I think you have a mean reversion system. One implementation problem maybe when a market is having a really bad day, dozens and even hundreds of your 500 stocks may hit level 2 within minutes. Does the messages queue up like in answering machine or does level 2 messages gets read first? If you have automated trading, you may incur long position in literally hundreds of stocks in a short time. I am guessing you are not ready for that. So it is best to have some manual practice and risk control in place before you think about automating it.
Although I rarely heard of "mean reversion", it is true that lot of executions occurred some day like in late August. Also most/all are long positions, as you understand my entry logic. As a beginner, I am not used to short still. Of course, if SnP500 drops 3%, then most of my alarm sounds as soon as particular stock 6%. If index shows 0%, then 3% drop of a stock makes sound. This number like 3% is just for explanation and quite difficult to calculate. It take hours to calculate 1000 entry point, mostly in the night a day before, by my program with thousands of line. Everyone has his own logic so that logic selection is not argument here. But thanks anyway since you understand fairly much for my personal entry logic. Hope to keep in touch, for possible future advance of "sounding work".
Furthermore, if some company offers me a sounding job as soon as MSFT hit some price, then I will gladly pay for it. Non-free commercial company like eSignal send me ONLY price, which I hate to pay.
You need normally not pay for this, as sounding an alarm when the price crosses a limit is a very easy task in any automated system. It requires a minimum script, maybe 10 lines of code. In Zorro a simple version could look like this: int n = 0; while(asset(loop(Assets))) { if(priceClose(0) >= limit[n] && priceClose(1) < limit[n]) sound("Alarm.wav"); n++; } But it would also work in a similar way in any other automated platform that you can connect to IB, such as Ninjatrader or TradeStation. If you can't code, there are many coders, me included, who could write such a script for you.