My sister wants to put up a video camera looking at her pool that way she can watch her son and his friends when they are over. That's not too hard, but what she asked was if I could make it come up on the cable on a channel. That way she turns to a channel on any TV in the house and sees the security feed.

So do you know of a device that lets me replace cable channel #2 (as fed from brighthouse/timewarner) with a video feed that I give it?

The cable service uses the Scientific Atlanta digital cable boxes.

any feedback is appreciated.

Check out channel vision They actually have a webinar on this. They have a few coming up.

The product is the Affinit Digital_Cable_Combiner

Radio shack has some modulaters,I don't think you can use channel 2 but the higher channels ,you inject the camera feed into the cable before it hits the digital box.

I've got a used Channel Plus 3025 unit if you are interested. It allows two inputs to two channels. There's nothing wrong with it, I just needed more inputs.
HERE is the link to the specifications.

Smarthome has what you want click here

Just make sure you get something that works on "DIGITAL CABLE".