Yeah, there have been a number of companies that have tried pushing fluid filled glasses, but I haven’t heard of many successes. Maybe because they are aiming for poorer countries, so don’t hit the media I consume.
Another adjustable lens I just learned about is an Alvarez lens pair that have complicated shapes which change the focal length as they are slid past each other. But the execution for the consumer market hadn’t been that great.
Obviously, there are many different kinds available online, but the link above also shows a cross section of the lenses.
