Tectonic TEAX19C01-8 19mm Metal Cup Exciter 8 Ohm

I really enjoyed playing with this with my 3rd grader. We used our own double sided tape so we could take it off and on a variety of surfaces. We eventually settled on the soundboard of a cheap classical guitar body(strings removed) which has been a great way to listen to flamenco or other stringed music. Sounds like you're sitting in the concert.

Great device! I have to add a usb rechargeable amp to give them enough power off of my Ipod. With the amp, they are loud and clear in my motorcycle helmet with road noise. Without, just slightly too low to hear the music well on the interstate.