Since a spy pen camera is mostly for the purpose of secretly capturing data (images, videos, or audio), it should be well-hidden. People should not know that you have a camera somewhere, recording whatever they are doing. It aside from being well-hidden, it should also be strategically hidden. This means that it should be positioned in a way that it has a clear view of the area, or at least of the particular place where you are protecting something. For example, if you have a safe in your office, you can position the camera in a way that is has a clear view of the whole office, or at least the place where the safe is.
In Your Pocket
A lot of people normally have a pen (or several pens) in their chest pockets. These people just want to be prepared that way. Having a spy pen camera in your chest pocket would not look suspicious. It would be better to have other normal pens as well, to make the discretion work even better.
On Your Office Desk
A spy pen camera would fit in on any office desk. Just make sure that you are able to position the spy pen strategically, as explained above. It would work best to include it in a collection of pens that all vary in terms of brand and appearance.
On A Book Shelf
It is quite normal to have a container with several pens in it on a book shelf. As long as the spy pen camera is not alone, it won’t look suspicious. As long as the book shelf allows the spy pen a good view, then there should be nothing to worry about. Pens are, thankfully, very common objects, so a spy pen camera would be fairly easy to hide.