There's been a lot written about MVSL. Oliver Sacks' book "Seeing Voices" is a good introduction, it has a chapter or maybe a whole section about it.
When I lived in Russia, a friend of mine spoke Russian sign language and I asked how they managed to communicate in the cold winter months outdoors. They told me using a lot of facial expressions, body language, and that you can sign a surprising amount even wearing gloves.<p>Mittens apparently are the equivalent of gagging somebody though.
A list of the ones that are being used in different regions/countries:<p>* <a href="https://en.wikipedia.org/wiki/List_of_sign_languages" rel="nofollow">https://en.wikipedia.org/wiki/List_of_sign_languages</a><p>* <a href="https://en.wikipedia.org/wiki/List_of_sign_languages_by_number_of_native_signers" rel="nofollow">https://en.wikipedia.org/wiki/List_of_sign_languages_by_numb...</a><p>Also, for the very young:<p>* <a href="https://en.wikipedia.org/wiki/Baby_sign_language" rel="nofollow">https://en.wikipedia.org/wiki/Baby_sign_language</a><p>Wonder if it'd be easier to create a 'universal' sign language than a universal spoken one (e.g., Esperanto, or an old <i>lingua franca</i> like Latin).