Give BTX Trader a try. We have a PC desktop client as well as a web version that we just released.

www.btxtrader.com

More info on how our stop limit order works:

Sell Stop Limit

Objective: Sell-stop orders protect long positions by triggering a market limit order if the price falls below a certain level. These orders are not guaranteed to be filled.
Example: You place a sell stop limit order with a stop price of $350 and a limit price of $375. When the last price at the exchange reaches $350, a limit order with price $375 is sent to the exchange by the BTX trade engine.

https://www.btxtrader.com/images/sell-stop-limit.png