This is a good topic and one that has been less of a problem for me the more I ride. I used to just not check except for the few times when the group stops for 10-15 minutes (usually about 2 times in a 3-6 hour ride). That was generally good enough, because since I lower my basals and don't take much insulin while riding, I simply don't have spikes or quickly dropping sugars. If you feel like you need to test often, than you may first want to reconsider your eating and insulin habits so that you can be more confident that your sugars aren't going to change quickly. If I feel low, I just grab my bottle filled with juice/soda and take a swig and I'm ready to keep riding. If I think I'm high (a much harder think to feel internally) and I don't expect the group to stop, I just let someone know I'm stopping and will catch up in a minute. It helps to spring ahead a little, jump off and check while they pass, and then catch up just a minute later.
I've been using a Dexcom for the past two years and that has changed everything for my while riding, especially now that I do very long rides up to about 160 miles so far. It doesn't always get the signal from my jersey pocket, but it gets it enough of the time and is accurate enough to know whether to eat, do nothing, or take a small bolus. I will usually still use a glucometer when the group stops to make sure that the Dexcom is still accurately tracking.
I'm a bit weary about testing while riding. That video showed her still weaving a bit, nearly slipping off the bars and the end, and only rolling along at a slow speed by herself. It's a different thing to do that moving at 17mph with a group, espcially if you have to focus on the meter and the bumps in the road that will throw you off. It just seems not worth the risk of falling or dropping the meter.