It also had a serial interface and an IR port for communicating with other devices.

Opposite of the IR port is a switch which, by default is set to switch between normal ringer operation and silent mode with vibration.

Why is there (apparently) an IR port on the front?

In addition to the IR port, there are three sensor input ports and three motor output ports (also usable for lamps, etc.).

An optional memory card with an IR port was available as an upgrade directly from Palm.

Infrared has significant limitations; one being that it is line of sight only; there had to be a clear space between the IR port and the controller.

However, in the US, a Verizon branded model does include the IR port.

The Palm III had an IR port, backlight, and flash memory.

You have to admire the tenacity of the guy who fought to keep the IR port on the X41.

Does anybody own devices with IR ports anymore?