We visited the archeology and Stone Age museum in Bad Buchenau http://www.federseemuseum.de/. For our visit we rented their audio guide system – they had one version for kids and one for adults. The audio guides were done very well and the information was well presented.
Nevertheless such devices break the joint experience of visiting a museum! We had three devices – and we stood next to each other listening but not talking to each other. Even though it may transport more information than the written signs it makes a poorer experience than reading and discussing. I wonder how one would design a good museum guide… There are plenty of projects but so far I have not seen the great solution.