It looks like infrared audioguides are older than I had previously thought. On 'Musematic' a few days ago, Loic Tallon published the first of a promised series of blog entries on handheld museum audioguides, including the link to a 1952 newsclip about the system developed by the Stedelijk Museum in Amsterdam. From what I see in the newsclip, it appears that the system uses an infrared transmitter to send signals to the handhelds, much the same way as the so-called 'cutting edge' Optima audioguides I wrote about a few months ago at 'Museum 3.0'.
This means that audioguides haven't really come that far since their childhood after the second world war.
I look forward to hearing more about this research project during the next few months. Great intitative, Loic!