Dips have been around for ever.. there are two primary types:
a) hands on a bench/table behind you. feet on another surface at about the same height.. you then dip down until your upper arm is parallel to the floor, and raise back up.
b) two parallel bars. one in each hand, arms fully extended, shoulders "racked" (stabilized.. not up by your ears).. then lower down till upper arm is parallel to the floor, press back up and repeat.

NOTES: .. for type A, you have to try it to see if you can do the movement pain free.. many people feel too much stress in the shoulder or in the elbow. unless it is pain free.. dont try it.
type b.. negative is that you need to be able to lift your body weight.. unlike type A, you are lifting your full body weight as you do not have part of your weight taken up by your feet resting on another surface.. I will also note that people do have shoulder or elbow irritation or pain from this..

Now that its explained. I will add that it probably will not do anything for the bat wings if it is excess skin. if it is lack of muscle tone, it can be an effective exercise, if you can do the exercise without pain.

After seeing her speak in person this weekend, I would highly recommend checking out Rachel Cosgrove's book or website.
http://www.rachelcosgrove.com/
her book is "the female body breakthrough" is is full of great advice. her and her husband run a facility out of CA, and are recognized as experts in training women in particular. My wife tried a Cosgrove workout and was very impressed by it.

hope i did not sound overly cautious.. just have seen a bunch of people who had shoulder problems or pain and dips were out of the question.