I started researching. I went on to Google Scholar and researched for some habits of senior Citizens, about buying and about behavior. First of all, it is more likely for them to use a tablet. The other important concept is that, if buying in the internet is challenging for them, shopping for canes or for medical appliances becomes a nightmare because they feel old. The upper side of this: Nobody has to see you buying a cane right?

I started to do a Low Fidelity Wire frame using paper and Sharpie. I made the whole thing but I pick this image since it is (for me) the best example of how my process works. I imagined to use the whole movement possibilities that a touch pad has, so if you see the paper on the left you can appreciate a man and a sign that rads Height. Well there is a scroll button that you can drag to adjust the height of your cane in comparison with your height. Also the bar below gives you more information about this.

Before even thinking about UI I went and made all the senior citizens I know, try this paper prototype. The idea of the Height selector was not well received. As it is, senior citizens are not fond of dragging, swiping or shaking their tablets or phones. They prefer clicks. Also large numbers, "as fewer options as you can and make the font nice and big".