Are you thinking about using a balance ball or balance ball chair at work? If you work in an environment where it is fairly laid back and relaxed then these are a great way of keeping your core tight and toned.
You might consider only using the balance ball or balance ball for part of the day in the morning or afternoon when you are not having any clients at your desk.
Your coworkers will get used to seeing this being used in the office and at other locations as well as more and more people realize how bad it is to be seated at in a chair for long hours and how great the stability ball and ball chairs are at helping your girdle muscles strong. These core girdle muscles are also responsible for a strong and healthy back muscles.
I prefer keeping my regular chair in tow for times when I need stability and can relax my body fully. But I keep this chair stowed away but nearby for times when I feel like using it.
Update: Ball chairs are no longer permitted at my workplace for safety reasons. You may want to ask your employer for permission before bringing one of these to work.