Trailing Stop Question

For those of you using trailing stops on options,
Do you base the stop on the option price or the underlying stock price?
and reasoning...

Thanks in advance..

Don't like trailing stops on Options, especially if I am relying on volatility of the underlying. 

Here's the problem with trailing stops on options;  Once the stop is triggered, you will be selling your option with a market order.  Depending on the bid ask spread of your underlying, you might get a very bad price.

Stocks normally have a narrow spread, so a market order will be within a couple cents of the price you'd expect.  Option spreads can sometimes be measured in dollars, depending on the liquidity.

Stop limit could add protection, but limit could be run through.  It's best to set a price alert, then manage your trade manually.