I agree that udundi has a lot to offer, and people of all physical ability levels can participate. It can be intense and fast for the younger or athletic people, but still effective as a softer art for older people and women (and men) who might feel uncomfortable with getting too aggressive.
As for me, I did fencing in the States many years ago, and then took up yoga (Ashtanga--the hard kind!) after a health crisis. For almost 9 years in Japan, I searched for the Japanese art that would be right for me and nothing really clicked until I serendipitously discovered the Motobu udundi dojo.
As an American, one of my favorite things is the lack of unnecessary formality. No incessant bowing, no "osu", restrained use of kiai, no strict senpai/kohai crap. In fact, Japanese people who join have to be told to lose some of the formality they naturally have--this might be different on Okinawa!
Of course there are other things that we are supposed to do, but the reasons are always clearly explained in terms of being considerate and staying alert, prepared, and healthy. Oh, and we are told to keep drinking water during practice, which is a big plus compared to other Japanese dojo obsessed with "gaman".
Udundi also has an essential ethical component different from the fundamentally servile concepts of bushido, based on what Uehara sensei I believe talked about as the "compassion" of the Ryukyu kings. I was kind of skeptical at first that a tradition rooted in the highest class of a feudal culture could have relevance today, but it is basically about how to act responsibly when in a position of power--something that people in the martial arts need to learn along with the physical aspect, and something Americans in particular should hear more of!