Origaudio Universal Rock-it 3.0 Portable Vibration Speaker with Rechargeable Battery 3.5mm - Black
I don't use this as much as I had thought I might it works great though and it super fun to show off.  I just wish the stickey pad were a bit cheeper to obtain from them, I have found a great solution though Glue Dots seem to do the job nicely its a bit more to carry around but I find I only take that with me when I wanna show it off so its not much more effort to grab the thing of glue dots too.  Just put tow or three of them down semi onto of each other and stick it on, Works Great!