Over at Mamapedia there are always great questions asked by many concerned parents. I found this one interesting, since it hits close to home for me! My daughter, who is the same age as the poster, also still has accidents, luckily, they are subsiding, as a result of the goal reward system.
At this age, after all medical venues have been exhausted, accidents usually are caused by the child not wanting to stop what they are doing, or perhaps feel they will get in trouble for asking, to go to the bathroom. A good thing to try, is to set a timer. From what others have said, as well as my own experience, a 2 hour timer works well, for the most part. Everytime the timer goes off, take your child to the bathroom. Working on rewards is good, but also work on taking things away. If they go to the bathroom when the timer goes off, put a sticker on a chart, that is working towards something the child wants (a toy, a special outing, a movie, etc...). But if they refuse or have an accident between that time, as a result of not letting you know they needed to go, put something they like to play with in a "time out." The length of the time out depends on you and what you feel would have the most effect on your child. Also, take off one sticker everytime, making the goal that much farther away.
Though this may not work for everyone, it will work for most kids. Rewards in and of themselves may lose effect over time, but reaching a goal is a lot different from a reward...something to look forward to!
Another great thing to add to this, is to talk it up. Constantly remind your child that they are a big kid, and talk up slumber parties (which could also be a goal reward), trips to big parks with friends, etc... The more you emphasize the positive, the more willing they will be to use the bathroom when they need to, and stop what they are doing!
Of course, this will not work for all children, and will not work right away, but it may have some positive effect and the results that you want for your child!
If you have anything to add or your own experiences to share, remember to share at www.myfourblessings.com!