The latest update of the PS Vita OS included a new camera function, which takes panorama pictures. It's the icon in the bottom middle.
The function differs from the one in my Samsung MV800 as you take separate photos instead of panning with the camera. You take the first photo by pressing the right button and then you just turn the Vita so that the next part is in the blue frame and the photo is taken automatically. The maximum is 9 photos, which will be stitched together when you finish.
Here are the first test photos. The photo below consists of three photos and looks actually quite good.
Then I tried full nine photos and that failed. There's a part missing between the first two photos. Using the function obviously requires some practice, but as the photo above shows, it does work, if you're careful.