Now this is just a super-cool use of technology. Cellphone's slosh and rattle reveal its contents is basically using shaking a cell phone of PDA with an accelerometer can produce sounds / images to indicate things like power level, number of emails, email senders, etc. Similar and different to the color based feedback that was proposed and partially implemented under the GNOME desktop (can't seem to find a link to anything specific about it right now, but it was proposing to use things like a green color in a download icon to represent good speed or orange or red for stalled downloads, stuff like that).