Hello,
Cisco SX20 have available DVI input interface for PC presentation or from any external video source. Usually handy cams have the HDMI or mini-HDMI out and you can take the signal from there and connect it to the DVI input of the SX20 using a HDMI/mini-HDMI to DVI cable. Note that the SX20 DVI input accepts maximum video resolution up to 1920x1080 @ 60 fps.
regards,
Ace