If you want prophetic, there's the '#minisec' from Arthur C. Clarke's 1975 novel _Imperial Earth_.
And of course #Orac from #Blakes7 in 1978.
Possibly only Kerr Avon truly twigged that all of the processing power was in the key and the big perspex box with the Christmas tree lights was a glorified base station with the PSU and speaker and simply camouflage for the most part.
https://mastodonapp.uk/@JdeBP/114587658010251638
Orac's key is now realizable as a #RaspberryPi with a 'modular' case from PiHut — I have one. It's the size and appearance of the BBC prop, connects to other computers wirelessly ('Tariel cells'), and has analogue audio output.
The popular #SciFi gadget that we don't have is the '#commlock' from #Space1999 in 1974. Unlike Orac, we have the technology to make full ones today. I suspect that they would go down a storm at SciFi conventions if someone set them up with a LAN, local videoconferencing, and electronic tickets/calendars.