Standing desks can be great. Ideally you want a sit to stand desk - one that allows you to change position as the most benefit is derived from movement and altering your position. It is not just sitting that is the new smoking, to be more correct - it is not moving that is the new smoking.
Standing for extended periods of time in one spot can be just as detrimental as sitting for sustained time periods. Desks with a fidget bar underneath are great however you don't need to go all technical. The easiest way to rectify this is to place a small step under your desk. A ream of paper or a brick will work fine. This way you can easily change position by placing one foot up on the step at a time.
In short: fidget more, shift your weight, rock side to side or backwards and forwards, suck your tummy in from time to time and make sure you do not end up slouching by leaning backwards and hyperextending your lower back.
Giving you my honest opinion on all things health related. Keeping it real and from the heart.