The iPAQ series of PDAs was first introduced in 2000 by Compaq with the H3100, a grayscale PDA running Pocket PC 2000. (See Windows Mobile) When HP acquired Compaq in 2001, they discontinued their own Jornada lineup in favor of the iPAQ. (See HP Jornada)
HP would continue to sell iPAQ PDAs for many years after this, and would become a major player at the height of the early 2000s PDA boom.
Also of note is that HP also released some iPAQ-branded smartphones running Windows Mobile.