I am not certain if something similar is already available out there. However, here's my own implementation of my simple idea of using the length of the candle-body, or wicks (high-low), to derive a Relative Volatility Index / Oscillator. In summary: When the R.CVI is significantly positive, it indicates a sudden increase in volatility; whereas, when the R.CVI drops significantly negative, it indicates a sudden decrease in volatility -- in relative to the (just prior) market trend.
If you do wish to copy, modify, and publish an alternate version base on this script, please do not plagiarize and kindly reference/link back to this original script. =D
Note: In no way is this intended as a financial/investment/trading advice. You are responsible for your own investment decisions and trades. Please exercise your own judgement for your own trades base on your own risk-aversion level and goals as an investor or a trader. The use of OTHER indicators and analysis in conjunction (tailored to your own style of investing/trading) will help improve confidence of your analysis, for you to determine your own trade decisions.