To achieve slow motion on play back you have to record at a high frame rate.
Most digital cameras struggle to get 30 frames per second (which is normal speed).
Some can record at 60 frames per second but only while in 320x240 mode.
There is one high speed digital camera that can probably do what you want.
It can record video at 1,200 frames per second.
It can take still photos at 60 pictures per second.
The Casio Pro EX-F1
Here is a link to a review:
It will cost you about $900
I've been searching for a couple of hours for digital cameras that have slow motion video capabilities. I was told Canon makes several but can't seem to find them. Can anyone suggest any cameras that can record and play back video in slow motion?