I've never heard of them either. I think i'd feel 'lopsided' and always be fidgeting with it to make sure it was in place (of course i seem to do that with the 2 pronged cannula's too)---- with my allergies i seem to have runny nose or plugged up nose (the 02 has dried up the runny quite a bit, which is a plus, altho now i can get 'too dry).
I think my problem would be with the tape. my skin is getting thinner & thinner & band aids can tear my skin off if i'm not careful in removing one....& my cheeks get sores from the cannula so i get the canula's with the earpiece foam; which i often wear across my cheeks, or switch it to ears if i start getting sores on ears. the one sided canula might actually help that problem though----it will be interesting to hear others opinions if they have ever used them.