Quint
The post Joffliver made re D4F may actually suit your need, as while they are notorious for shifting their prices with spreads and bias, their Daily CASH Dow tracks the actual index within 2 or so points throughout the day, so you could set the alert for either the bid or offer and know that the actual index price was only a couple of points away. Also, if you have predetermined your entry or exit you can easily set your limit order and alarm call at the same time.
The problem then is that when you get your message you may be prone to leap in the air with joy at the cash you know you've just made - and who knows where you may be at the time!