Theory :
Sylvain Vervoort's article in May 2008 issue of TASC , "The Quest For Reliable Crossovers," describes a trading system based on three functions: the triple exponential moving average (TMA), the heikin-ashi close (haC), and the "typical price" (TypicalPrice). Vervoort's strategy trades the crossover of the typical price and heikin-ashi TMAs
In order to make it easier to spot the trend changes, this version is made as a separate window histogram indicator
Usage :
You can use color changes as signals

PS:
The Vervoort's crossover indicator "counts" ion the lag of the heiken ashi "average: price, hence, if you re changing that some more experimenting with periods and different price types is advised. For the sake of being be to experiment the full set of heiken ashi prices is provided :
Vervoort's crossover - tape
Vervoort's crossover - tape
Vervoort's crossover - extended
Vervoort's crossover - extended