Drill Bit Accessory Identification

Well, I don't think you will buy such thing again in the next years, so I suggest that you consider it a major purchase and plane for all reasonable usecases, not only for laying cables. You can use it later for all sorts of inspections - finding sources of noise, finding sources of leaks, finding clogs in ducts and sewers, etc.

I believe ability to take pictures can be worth it - you can post a picture here and ask if that's mold or you can send it to the utility company to convince them that it's a leak on the common property and not on yours or you can use it to post something really curious to your twitter/facebook/whatever account. You decide whether these usecases are worth considering and how often you might encounter them.

One very important thing is you have to actually test how the thing works. It may be that it saves pictures of infernal quality that can only be used as garbage.

While this can be done with a Dremel (I've done it), you'll get a much better result picking up a paddle bit or hole saw and a hand drill. If the exactness of 1.125" is not particularly required, you can go with the dremel, but if you need exactly that hole size (say, you're trying to minimize possible air leaks in something) I'd say you need a drill.

Edit: I just realized you're using a dremel on plastic -- This will lead to bits of high static plastic everywhere. In addition to that, whatever you cut will not have clean cuts, there will be melted plastic all the way around the edge. I won't say this isn't an irreparable situation, but getting a drill probably is your best bet.

Aside from that, almost any home based project will be 100x easier with a drill. It's one of the few tools even the least DIY people should have around the house.