While this is a wonderful and clever feature for the iphone, I strongly encourage you to use it for entertainment purposes only.   Massage if done incorrectly could cause harm.  That being said…I highly doubt that a vibrating phone would cause harm to you or anyone playing with your phone but it does illustrate the point of just letting the professionals do the work.  Clever feature….non clever results.

Update: It appears a similar feature is available for the XBox 360.

Here is an article that briefly explains how massage therapy works…if you were ever curious as to the physiology of it, this is a good explanation

http://www.emaxhealth.com/1/6/26055/benefits-professional-therapeutic-massage.html