If you compare it to today's technology!

There were other Psion portable computers - but at a stretch you could call them pocketable (if you were wearing clown trousers).

The Psion 3 was the first attempt to resemble something like a computer - (e.g. usable qwerty keyboard).

I had one of these devices and have to say at the time it did a lot of things very well; contact manager, database manager, wordprocessor, spreadsheet and it's own programming language.

It also had solid-state disks (expensive), serial cable and an optional printer cable too.

Then there was the huge amount of software for it.

Atari also brought out the "Folio" at the same time?
Can't remember which one was first though.