StreamOfTheSky
Adventurer
There's a feat in PHBII called Deadeye shot. To use it, you ready an action to fire a missile at a target that has just been struck by an ally. The target looses his dex bonus against your readied shot. There is no range limit on applying sneak attack from this feat.
This is misleading. You still need to be within sneak attack range in order to sneak attack. And Deadeye Shot doesn't give you a sneak attack when someone is hit in melee. It makes your readied attack catch the foe flatfooted, or makes him lose dex to AC (which isn't always the same thing, in regards to Uncanny Dodge, etc...), I forget. Which means that if you're within range, it should be a sneak attack.