Mike,
Another low tech solution you (and others) might like to pursue...
I take a lot of panoramas, and being level is as much a problem in a panorama as it is in a telephoto shot (arguably worse!).
I don't have a particularly expensive or sophisticated tripod.
When I set up for a panorama, I sweep the shot and watch what the verticals and horizon are doing at each extreme and centre of the planned pano field. I then adjust the legs of my tripod, not the head, so the horizon stays flat across the image, and verticals stay vertical at the extremes. With a bit of practice this can be done quite quickly. I reckon it world be rare from me to take more than a minute to level my tripod for a pano! I usually watch the view finder or camera screen while adjusting.
The same procedure could be used to level for a telephoto shot... if you are perceptively level over 180 degrees - even in a the preview screen - you are going to be very close in a single photo!
Thinking about this a bit, I think the fact that my tripod doesn't have a ball head is significant because I can get my camera square to the vertical axis of the tripod very easily.
The important part of this, I think, you should keep in mind is adjusting the legs of the tripod. A small adjustment to the leg of the tripod is an even smaller adjustment at the camera, so you can be very precise. While a ball head might be convenient, I imagine a small adjustment on the ball head results in a larger adjustment at the camera... those of you with ball head tripods feel free to correct me if I am sprouting fertilizer!
Hope this helps (even if you have a ball head tripod!)
Al.