Mobile magic posts the wait times that are posted at the doors of the attractions. Many find these to be off at times (esp near opening and closing). Mobile Magic is verizon exclusive and on a limited number of phones.
Some other phone apps post actual wait times like with a timer that people use in line and average out the posts of what is reported at the door and what people are actually reporting. We find this more accurate but not 100% all the time. The one we use most often and found the most accurate is Lines. And it will work with iphone and many other smart phones on any carrier (with data).