Order type in options using Underlying Price level

[eastside]

One of the new additions in options is addition of Limit Orders which is great start because there was no way to enter and exit positions at a given price before.

My suggestion in addition to that is it would be more useful to trigger the order when the underlying reaches a certain level because the implied volatility would be constantly changing (mostly increasing thru the day) which means the price for the strike is fluctuating higher and therefore the LIMIT order will potentially never execute. however if I could say buy this particular option when the underlying, say US500 is at 5350, would be clearer to enter and exit.