I'd say if you are hell-bent on not doing abs...then this would be better than nothing.
But I think those Electronic Muscle stimulators are made more for the smaller supporting muscles, not large muscles like the abdominals.
When I had shoulder surgery, those EMS machines were part of my rehab program, before I moved on to light weight training. I think that was just to strengthen the core shoulder muscles (rotator cuff, etc...), not to strengthen my delts or anything like that.