I've used Smartballs and they are fun, but I didn't feel like they had much effect (beyond just what I get from kegeling). I found them to be more of an entertainment device than something useful for exercises.
I do most of my kegeling while driving to and from work, and most insertable "aides" work best if you are standing or lying down, so they are not very useful for exercising while commuting. Smartballs, ben-wah balls, and jade eggs all require gravity; it is the weight of the balls etc. that provides the exercise (you have to kegel to keep them inside) and they don't do much if you're sitting. Other vaginal exercisers that you insert and squeeze (like KegelMaster) have parts that stick out, so you can only use them lying down in a bed. I expect that the latter work very well, but I simply don't have the privacy to use one so I've never invested in one. I confess that I am curious, though!
