I see that there are software trading platforms that offer real-time alerts based on price (open, close, last), volume, etc. These are limited in their usage and do not meet the needs of my intentions. Does anyone know of any trading platforms that are free of cost and that will offer alerts based on the value of a particular technical indicator or user-defined ones? For example, suppose that I have opened a position and want to generate a sell signal alert when the MACD(26,12) has decreased in value from its prior trading period: DeltaMACD(26,12) < 0.