Shaking cellphones reveal what's inside

Cellphone users could soon tell when their handset is running low on juice or laden with new messages simply by reaching into their bag or pocket and giving it a quick shake.

http://www.youtube.com/watch?v=AWc-j4Xs5_w

http://technology.newscientist.com/article/dn12970-cellphones-slosh-and-rattle-reveal-its-contents.html