The distance between the price of a security and Linear Regression Trend line gives the basis to measure Standard Error. The trend is as strong, as close the price is to the Linear Regression Trend line. The higher the distance is, the weaker and less reliable trend is due to the high standard error.
High price volatility is indicated by high values of Standard Error. Trend modification is followed by an immediate standard error growth.
The combination of this indicator and the R-Squared is widely used. R-Squared decrease along with Standard Error generally forecast trend changes. The unusual values trending to a converging are the sign of change.
Still a downward movement from the top is not the only direction of the trend change as far as sideways fluctuations are supposed to be the change either.