*** [Updated July 11, 2014: See below for DEnvelope %B and Bandwidth scripts to go along with this DEnvelope] ***
Bollinger Bands (BB) usually expand quickly after a volatility increase but contract more slowly as volatility declines. This extended time it takes for BB to contract after a volatility drop can make trading some instruments using BB alone difficult or less profitable.
In the October 1998 issue of "Futures" there is an article written by Dennis McNicholl called "Better Bollinger Bands", in which the author recommends improving BB by modifying: - the center line formula & - different equations for calculating the bands.
These bands, called "DEnvelope", follow price more closely and respond faster to changes in volatility with these modifications.
Fore more indicators, check out my "Master Index of indicators" (Also check my published charts page for new ones I haven't added to that list): tradingview.com/v/4IneGo8h/