Newton

The Newton platform was Apple's first attempt in the handheld market. The devices ran Newton OS.

Hardware models
From Apple:
 * MessagePad (also known as the H1000, Original MessagePad, or OMP)
 * MessagePad 100 (same hardware as OMP, but with newer version of Newton OS)
 * MessagePad 110
 * MessagePad 120
 * MessagePad 130
 * eMate 300
 * MessagePad 2000
 * MessagePad 2100

From Motorola:

From Sharp:
 * Sharp ExpertPad PI-7000 (based on the Original MessagePad)
 * Sharp ExpertPad PI-7100 (based on the MessagePad 100)

From Digital Ocean:
 * Tarpon
 * Seahorse

From Siemens:
 * Siemens Note Phone

From Harris:
 * Harris SuperTech 2000 (based on the MessagePad 130)

Discontinuation
The Newton project was briefly spun off from Apple Computer into a wholly-owned subsidiary company, Newton Inc., but was reabsorbed in July 1997 when Apple CEO Gil Amelio was fired by the board and Steve Jobs took over as interim CEO. Jobs cancelled the Newton in 1998, causing fans and developers to protest at the Apple campus in March.

Two ex-Apple Newton developers later founded Pixo, the company that created the operating system for the original iPod.