X_DEV is a complete system based on "deviation bands" that are not only constructed differently from Bollinger Bands, but are also used to find a percentage amount that is necessary for the calculation of how much a person should use towards the next best buy or sell signal that X_DEV generates. Everything is tied in together (read....."system") to produce a trading methodology that the user can use to successfully enhance their overall performance.
The use of Bollinger Bands by themselves (which by the way will lead to waaaaay to many buy or sell signals.....see chart below) is not a system at all. It just another technical indicator. Now, I realize in you earlier post you suggested "filtering" with the RSI indicator, but again you are just generating signals based on standard technical analysis. There are a zillion different ways to generate buy or sell signals based on technical indicators. Just as there are a zillion systems that will tell you when to buy or sell.
The whole point of X_DEV is to not be like the zillion or so indicators or systems that tell you to plunk down all your cash on a play and hold till the next sell signal is reached. In my view that is entirely too risky for most traders, and also not as effective in the long run.
The point is to have a balanced systematic mechanical approach, that will allow you to average into an investment (in partial amounts) when it is timely to do so, and average out in partial amounts when it is timely to do so. The system must have parameters that compliment and react off of each other to produce optimal results.
The use of any standard technical indicators alone or together without the cash management properties of a balanced systematic approach seems far inferior in my opinion.
Of course you can try and prove me wrong by displaying some hard evidence, in the form of a spreadsheet or other verifiable results if you wish, that I am incorrect, or that you have a "better way". I have posted more than words that prove X_DEV is a viable system. If you or anyone else can also post more than words, then by all means please do so.
Also, please give the people that come to this board the benefit of doubt that they know how to make their own decision regarding the purchase of X_DEV or not, without suggesting otherwise. I am sure they are all adults and wise enough to make their own decisions.