
It's the one in the middle, in case you can't tell.
The Simon, codename "Angler", was developed by IBM, manufactured by Mitsubishi, and marketed by BellSouth. It ran a graphical interface on top of the Datalight ROM-DOS system, on a 4.7" monochrome screen, with the super-high resolution of 293x160. It had a very powerful 16 MHz CPU, a generous whole 1MB of RAM and another 1MB of storage, and a blazing-fast 2400bps modem! Additional programs could be added through the PCMCIA slot. Its incredible battery allowed for an hour of speech or 8 hours in stand-by. And all this in a diminutive device of just half a kilogram!

For the stubborn 5% of the world, that's around 18oz or 1.1 pound.
The price? Dirt cheap, just $1100. Or $1770, adjusting for inflation. What a deal!

IBM's Frank J. Canova Jr., the creator.
But what was so special about it? Most cell phones at the time were strictly phones. Simon, however, had PDA functions: contact list, calendar, calculator, notepad... but perhaps what truly defined it as a smartphone was the fact that it was possible for the user to install applications. OK, so only one third-party program was released, a remote desktop solution that cost more than the device itself, but anyway...
The technical limitations and the price got in the way, and a cameo in the movie "The Net" came too late to help: only 50,000 units were sold. The Simon was canceled in February 1995; at the time in the middle of a massive reorganization, IBM chose not to launch its smaller and improved successor, codename "Neon".

Not that this bomb could have helped much anyway.
Note that, given its primitive nature, and utter commercial failure, many dismiss the Simon and instead regard the Nokia 9000 Communicator as the first device deserving of the name "smartphone". You be the judge.

Of course it's more advanced, duh. It came out two years later.