Here is an update on the Daily VXX Trend Model:
On the close-up below, notice how trend line support held prices on two occasions before VXX ran higher both times:
I've seen this trend line support work often enough to consider it a low-risk strategy. In other words, for any symbol, initiating a trade in the direction of the major trend whenever prices retrace to near the trend line allows for an entry with a very tight stop, i.e. prices violating the trend line.