They're designed to help you hit long shots from short or wispy rough. Long irons don't have the loft to allow you to do this and get tangled in the grass. The shape of the rescue wood does allow this with a nice high flight because they typically have a 19 or 21 degree loft.
They're good off the fairway too but the shafts are shorter than say a 5 wood so they don't go so far.
I use cobra bafflers in place of my 3 and 4 irons. I think that they are excellent, I find them oh so easy to hit and they seem to give me a hiher degree of accuaracy. Long irons are my main weakness and on a long par 3 or with 175 left to the green the bafflers are king for me.