A script driven countdown clock overlayed on top of video.

Hi,

I'm working on a multi screen video for a corporate lobby. The video will span a few screens with various company related images and video clips. The client wants a large countdown clock across the video that counts down over the course of a few weeks leading up to an event. (example: 01:09:15:59)

I have someone working on the clock. My question is, what hardware, software or company can stream the video and combine the clock on top of the video. I have to stress that the clock must be live as it counts down to a real event.

Thanks in advance. -Dan