A Java virtual machine, the mobile browser STNC HitchHiker[3] and synchronizing software for Microsoft Windows was bundled with the 5mx as optional installations and, later, the Executive Edition of the 5mx was bundled with various hardware and software extras including version 3.62 of the Opera web browser and a mains electric outlet adapter.

A wealth of third-party software was also available, including games, utilities, navigation, reference, communication, and productivity applications, and standard programming tools like Perl and Python.

Psion's experience designing for this form factor and attention to detail made these machines a favourite with power users, many of whom kept using them, despite their age and the appearance of Symbian OS for mobile phones and other PDAs with more impressive specifications.

In 2017, a team of original Psion engineers created a startup company, Planet Computers, to make an Android device in a similar form factor, the Gemini (PDA).

The Cosmo Communicator is a development of this device, enhancements including an external touchscreen on the rear of the clamshell lid, mainly to facilitate use as a mobile phone without opening.