Years ago, I corresponded with John Ehlers and asked
him about his indicators. The result was, among
other things, the attached experimental indicator.
These are bands built on Ehlers's instantaneous trendline.
Two bands are linear, a la Keltner, and two are nonlinear,
a la Bollinger. Looking at it, the only advantage
of this indicator is probably its stability in the sense
that it doesn't recalculate / repaint.

As a side note: Ehlers codes his indicators in EasyLanguage
and often uses trigonometric functions. The measure of an angle
in EasyLanguage is degrees, while in MQ4, it's radians.
So, for example, 180 degrees in EasyLanguage must
be translated into Pi in MQ4.

The indicator is highly experimental, so for now, I have
decided that access will be limited until the end of August.